CN106133170A - High-carbon hot-rolled steel sheet and manufacture method thereof - Google Patents
High-carbon hot-rolled steel sheet and manufacture method thereof Download PDFInfo
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- CN106133170A CN106133170A CN201580016876.8A CN201580016876A CN106133170A CN 106133170 A CN106133170 A CN 106133170A CN 201580016876 A CN201580016876 A CN 201580016876A CN 106133170 A CN106133170 A CN 106133170A
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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
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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
- 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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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—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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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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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
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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- 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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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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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
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/003—Cementite
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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
- C21D2211/005—Ferrite
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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
- C21D2211/009—Pearlite
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Abstract
The present invention provides a kind of high-carbon hot-rolled steel sheet, its using be added with B steel as blank, it also is able to stably obtain the quenching degree of excellence even if carrying out in blanket of nitrogen anneals, further, there is before Quenching Treatment hardness and be calculated as less than 73 and processability that percentage of total elongation is more than 39% such excellence with HRB.Described high-carbon hot-rolled steel sheet has following composition: contain in terms of quality %: C:0.20～0.40%, below Si:0.10%, below Mn:0.50%, below P:0.03%, below S:0.010%, below sol.Al:0.10%, below N:0.0050%, B:0.0005～0.0050%, contain the Sb adding up to 0.002～0.030% further, Sn, Bi, Ge, Te, in Se more than a kind, solid solution B amount ratio shared by B content is more than 70%, and have and be made up of ferrite and cementite and cementite density in above-mentioned ferrite crystal grain is 0.08/μm2Following micro-assembly robot, hardness is calculated as less than 73 with HRB, and percentage of total elongation is more than 39%.
Description
Technical field
The present invention relates to high-carbon hot-rolled steel sheet and manufacture method thereof.Particularly to the nitriding suppression being added with in B and top layer
Effect height, processability and the high-carbon hot-rolled steel sheet of quenching degree excellence and manufacture method thereof.
Background technology
Now, the automotive part such as gear class, fluid drive box part, seat harness parts will be mostly in order to belong to
In JISG 4051, the hot rolled steel plate of the frame for movement carbon steel steel of regulation is true after utilizing cold working to be processed into desired shape
Hardness desired by guarantor, implements Quenching Treatment and manufactures.Therefore, become the hot rolled steel plate of blank need excellent cold-workability,
Quenching degree, and up to the present there has been proposed various steel plate.
For example, Patent Document 1 discloses a kind of cold working intermediate carbon steel sheet, it was carried out with 100 DEG C/sec averagely add
Thermal velocity keeps 10 seconds being quenched the high-frequency quenching to room temperature with the average cooling rate of 200 DEG C/sec at 1000 DEG C after heating up time
Hardness is 500HV～900HV, in terms of quality %, containing C:0.30～0.60%, Si:0.06～0.30%, Mn:0.3～
2.0%, below P:0.030%, below S:0.0075%, Al:0.005～0.10%, N:0.001～0.01%, Cr:0.001
～0.10%, or contain further Ni:0.01～0.5%, Cu:0.05～0.5%, Mo:0.01～0.5%, Nb:0.01～
0.5%, 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%, more than a kind of Sn:0.003～0.03%, Sb:0.003～0.03%, As:0.003～0.03%, and its carbide
Average diameter d be below 0.6 μm, spherical rate p of carbide is 70% less than 90%, above-mentioned carbide average
Spherical rate p% of diameter d μm and above-mentioned carbide meets d≤0.04 × p-2.6, or its hard before cold working further
Degree is that 120HV is less than 170HV.It addition, in patent documentation 1, as the manufacturer of such cold working intermediate carbon steel sheet
Method, discloses following method: after the steel of above-mentioned chemical composition is held in 1050～1300 DEG C, carries out at 750～1000 DEG C
The lower hot rolling terminating rolling, after being then cooled to 500～700 DEG C with the rate of cooling of 20～50 DEG C/s, cold with 5～30 DEG C/s
But the temperature that speed is cooled to specify is batched, after keeping under conditions of regulation, with 600 DEG C～Ac1The temperature of-10 DEG C
Annealing.
It addition, Patent Document 2 discloses a kind of steel plate adding boron, described steel plate, in terms of quality %, contains: 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 contain further 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%, a kind or 2 kinds in Sn:0.003%～0.03%, Sb:0.003%～0.03% and As:0.003%～0.03%
Above composition, its mean concentration of the solid solution B in region till 100 μm from top layer to the degree of depth is more than 10ppm.It addition,
Patent Document 2 discloses when annealing in the atmosphere based on nitrogen, the phenomenon inhaling nitrogen can be manifested, from the viewpoint of quenching degree
The B N in steel in annealing being considered as important element is combined formation BN, solid solution B minimizing and cannot guarantee through hardening based on B
Property improve effect.Patent Document 2 discloses in order to ensure quenching degree, need to make to be the district till 100 μm from top layer to the degree of depth
Solid solution B in territory is more than 10ppm, it is therefore important that suppress the shadow of the atmosphere of the heating in manufacturing process, annealing operation
Ring.It addition, in patent documentation 2, as the manufacture method of the steel plate of such interpolation boron, disclose following method: at 1200 DEG C
After steel to mentioned component composition heats below, carry out hot rolling with the final rolling temperatures of 800～940 DEG C, then to cool down speed
After 20 DEG C/more than s of degree is cooled to less than 650 DEG C, batch with 20 DEG C/s cool below and at 400～650 DEG C, pickling
After, it being more than 95% at hydrogen and be less than-20 DEG C to the dew point of 400 DEG C, the dew point of more than 400 DEG C is the gas of less than-40 DEG C
In atmosphere, with 660 DEG C～Ac1Temperature anneal.It addition, in patent documentation 2, further disclose in above-mentioned pickling laggard
Row is cold rolling or implements cold rolling after above-mentioned annealing, and then with Ac1～Ac1The temperature of+50 DEG C is annealed, and slow cooling is to Ac1-
Till 30 DEG C.
Prior art literature
Patent documentation
Patent documentation 1: No. 5048168 publications of Japanese Patent No.
Patent documentation 2: No. 4782243 publications of Japanese Patent No.
Summary of the invention
In terms of obtaining good cold-workability, high-carbon hot-rolled steel sheet is required than relatively low hardness and high elongation rate.Example
As, in the past, towards to being made by heat, cut, the steel plate that is fabricated by of multiple operations such as welding colds pressing and one-body moldedization
The purposes of the automobile component etc. made, it is desirable to hardness is calculated as less than 73 with Rockwell hardness HRB, and percentage of total elongation (El) is more than 39%
Etc. characteristic.It addition, have compared with soft and high elongation rate for this kind and make the good high-carbon hot-rolled steel sheet of processability, it is desirable to excellent
The Vickers hardness of more than HV440 is obtained after different quenching degree, such as expectation water quenching.
In the technology of patent documentation 1, quench-solidifying in order to ensure during the high-frequency quenching of average heating rate 100 DEG C/sec
Can, the average diameter of carbide is set to below 0.6 μm, but the steel containing substantial amounts of C that C content is 0.3～0.6% etc
In, it is below 0.6 μm owing to the mean diameter of carbide attenuates, so the density of carbide becomes big, easy high intensity, having can
Can processability reduce.It addition, as its manufacture method, carry out the cooling in 2 following stages and control, i.e. after hot rolling with 20～
After the rate of cooling of 50 DEG C/s is cooled to 500～700 DEG C, cool down with the rate of cooling of 5～30 DEG C/s, exist and be difficult to manage
The problem that cooling controls.
The technology of patent documentation 2 is also carried out following 2 stages cooling control, the most after hot rolling, with rate of cooling 20 DEG C/
After more than s is cooled to less than 650 DEG C, cool down with 20 DEG C/below s, exist and be difficult to control to the problem that cooling controls.Additionally,
In the technology of patent documentation 2, in order to improve quenching degree, add the Mn of more than 0.5%.Although Mn makes quenching degree improve, but because of
Solution strengthening and make the intensity of hot rolled steel plate itself increase, make hardness become big.
On the other hand, as adding the element making quenching degree improve with trace, it is known to B, but also like institute in patent documentation 2
As record, if annealed in the atmosphere of main body by the nitrogen being typically used as atmosphere gas, then there is solid solution B
The problem that the quenching degree reduced and cannot obtain being produced by B improves effect.In patent documentation 2, for such problem, by
The atmosphere of the hydrogen containing more than 95%, maybe this hydrogen is replaced in the atmosphere of the non-active gas such as Ar carries out annealing solving, but
The cost using the heat treatment of these gases uprises.It addition, and indefinite only by this technology, can be in the annealing in blanket of nitrogen
Nitrogen is inhaled in suppression.
In order to solve the problems referred to above, it is an object of the invention to propose high-carbon hot-rolled steel sheet and manufacture method, described height
Carbon hot rolled steel plate using be added with B steel as blank, even if annealing in blanket of nitrogen, it is also possible to stably obtain excellence
Quenching degree, and before Quenching Treatment, have that hardness is calculated as less than 73 with HRB, percentage of total elongation is adding of more than 39% such excellence
Work.
The present inventor etc. are to Mn content being set to less than 0.50% this Mn amount fewer than conventional steel and being added with the high of B
The relation of the manufacturing condition of carbon hot rolled steel plate and processability, quenching degree is furtherd investigate, and result obtains following opinion.
I) the cementite density in ferrite crystal grain is to the hardness of high-carbon hot-rolled steel sheet before quenching, percentage of total elongation (below,
Also referred to as percentage elongation) impact is greatly.It is calculated as the hardness of less than 73 with HRB, the percentage of total elongation of more than 39% to obtain having
(El) steel plate, needs the cementite density in ferrite crystal grain is set to 0.08/μm2Below.
Ii) after the Finishing temperatures in the finish rolling of hot rolling and finish rolling rate of cooling to 700 DEG C to ferrite crystal grain
Interior cementite Effects of Density is big.If Finishing temperatures is too high or rate of cooling is too small, in steel plate the most after hot rolling, nothing
Method obtains the steel plate of the tissue containing the pro-eutectoid ferrite volume fraction with pearlite and regulation, difficult after spheroidizing
To reduce cementite density.
Iii) by least one in Sb, Sn, Bi, Ge, Te, Se is made an addition in steel, even if thus real in blanket of nitrogen
When executing annealing, it is also prevented from nitriding, suppresses the reduction of solid solution B amount to obtain high-hardenability.
The present invention is carried out based on such opinion, and using following as purport.
[1] a kind of high-carbon hot-rolled steel sheet, it has following composition: contain in terms of quality %: C:0.20～0.40%, Si:
Less than 0.10%, below Mn:0.50%, below P:0.03%, below S:0.010%, solid solution aluminum (sol.Al): 0.10% with
Under, below N:0.0050%, B:0.0005～0.0050%, contain further add up to 0.002～the Sb of 0.030%, Sn,
In Bi, Ge, Te, Se more than a kind, remainder is made up of Fe and inevitable impurity, and solid solution B amount is shared in B content
Ratio be more than 70%, the cementite density having in ferrite crystal grain that be made up of ferrite and cementite, above-mentioned is
0.08/μm2Following micro-assembly robot, hardness is calculated as less than 73 with HRB, and percentage of total elongation is more than 39%.
[2] according to the high-carbon hot-rolled steel sheet described in above-mentioned [1], wherein, in terms of quality %, contain further and add up to
In Ni, Cr, Mo of less than 0.50% more than a kind.
[3] according to the high-carbon hot-rolled steel sheet described in above-mentioned [1] or [2], wherein, above-mentioned it is made up of ferrite and cementite
The average diameter of the 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] manufacture method of a kind of high-carbon hot-rolled steel sheet, after it will have the following hot roughing of steel formed, with finish rolling temperature
Degree: Ar3Transformation temperature～870 DEG C carry out finish rolling, are cooled to 700 DEG C with the average cooling rate of 25 DEG C/s～150 DEG C/s, to batch
Temperature: 500 DEG C～700 DEG C are batched, thus manufactures and has pearlite and be calculated as the proeutectoid ferrite of more than 5% with volume fraction
The steel plate of body, then at Ac1Below transformation temperature annealing this steel plate, above-mentioned composition is to contain in terms of quality %: C:0.20
～0.40%, below Si:0.10%, below Mn:0.50%, below P:0.03%, below S:0.010%, sol.Al:0.10%
Below, below N:0.0050%, B:0.0005～0.0050%, contain further add up to 0.002～the Sb of 0.030%, Sn,
In Bi, Ge, Te, Se more than a kind, remainder is Fe and inevitable impurity.
[5] according to the manufacture method of the high-carbon hot-rolled steel sheet described in above-mentioned [4], wherein, above-mentioned steel, in terms of quality %, enters one
Step is containing more than a kind in Ni, Cr, Mo of 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 is suitable to blank steel plate needs the automotive parts such as the gear class of cold-workability, fluid drive box part, seat harness parts.
Detailed description of the invention
Hereinafter, high-carbon hot-rolled steel sheet and the manufacture method thereof as the present invention is described in detail.Should illustrate, as long as
It is not particularly illustrated, then as " % " expression " quality % " of unit of component content.
1) composition
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 is impossible to by becoming
Type is that the heat treatment after parts obtains desired hardness, specifically, can not get the hardness of more than HV440 after water quenching.
Accordingly, it would be desirable to C content is set to more than 0.20%.On the other hand, if C content is more than 0.40%, then steel plate hardening, cold rnning
Work is deteriorated.Therefore, C content is set to less than 0.40%.In order to obtain high quenching hardness, preferably C content is set to 0.26%
Above.By C content is set to more than 0.32%, it is possible to stably obtain the water quenching hardness of more than HV440, thus more excellent
Choosing.
Below Si:0.10%
Si is the element being made intensity increase by solution strengthening.Because along with the increase of Si content and hardening and cold working
Property be deteriorated, so Si content is set to less than 0.10%.Si content is preferably less than 0.05%, and more preferably less than 0.03%.
Si makes cold-workability reduce, and therefore Si content is the fewest more good, if but exceedingly reduce Si, then refining cost increases, therefore Si
Content is preferably more than 0.005%.
Below Mn:0.50%
Mn is the element making quenching degree improve, and on the other hand, is also the element being made intensity increase by solution strengthening.If Mn
Content is more than 0.50%, then the excessive hardening of steel plate and cold-workability reduce.The banded structure additionally caused by the segregation of Mn expands
Exhibition, tissue becomes uneven, therefore has hardness, the deviation of percentage elongation becomes big trend.Therefore, Mn content is set to 0.50% with
Under.Mn content is preferably less than 0.45%, and more preferably less than 0.40%.Should illustrate, lower limit does not specify, in order to
The precipitation of suppression graphite, and when Quenching Treatment heats, the whole C solid solutions in steel plate are obtained the quenching hardness of regulation, preferably
Mn content is set to more than 0.20%.
Below P:0.03%
P is the element being made intensity increase by solution strengthening.If P content is more than 0.03%, then the excessive hardening of steel plate and
Cold-workability reduces.It addition, because reducing the intensity of crystal boundary, so the degraded toughness after Cui Huo.Therefore, P content is set to
Less than 0.03%.In order to obtain excellence quenching after toughness, preferably P content is set to less than 0.02%.Because P makes cold working
Property and quenching after toughness reduce, it is advantageous to P content is the fewest more good, if but make P reduce more than necessity, then refining cost
Increasing, therefore P content is preferably more than 0.005%.
Below S:0.010%
S because formed sulfide and make high-carbon hot-rolled steel sheet cold-workability and quenching after toughness reduce, so must not be
Nondecreasing element.If S content is more than 0.010%, then the cold-workability of high-carbon hot-rolled steel sheet and quenching after toughness notable
It is deteriorated.Therefore, S content is set to less than 0.010%.For the toughness after obtaining excellent cold-workability and quenching, S content is excellent
Elect less than 0.005% as.Because the toughness after S makes cold-workability and quenching reduces, so S content is the fewest more good, but such as
S is reduced more than necessity by fruit, then refining cost increases, and therefore S content is preferably more than 0.0005%.
Below sol.Al:0.10%
If sol.Al content is more than 0.10%, then generating AlN when the heating of Quenching Treatment, austenite crystal is the most micro-
Refinement, can promote during cooling that the generation of ferritic phase, tissue become ferrite and martensite, and the hardness after quenching reduces.Therefore,
Sol.Al content is set to less than 0.10%.Sol.Al content is preferably less than 0.06%.Should illustrate, Al has deoxidation effect
Really, in order to be sufficiently carried out deoxidation, preferably sol.Al content is set to more than 0.005%.
Below N:0.0050%
If N content is more than 0.0050%, then because more than necessity forming BN so solid solution B amount reduces.Further, since shape
Become necessary above BN, AlN, so the excessive miniaturization of austenite crystal when the heating of Quenching Treatment, ferrum during cooling, can be promoted
The generation of ferritic phase, the hardness after quenching reduces.Therefore, N content is set to less than 0.0050%.N content is preferably
Less than 0.0045%.Should illustrate, lower limit does not has special provision, but as it has been described above, N forms BN, AlN.If formed suitably
BN, AlN of amount, then these nitride suitably suppress the coarsening of austenite crystal when 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 improving quenching degree.The condition of the rate of cooling after finish rolling in hot rolling based on the present invention
Under, when B content is less than 0.0005%, makes the solid solution B amount deficiency that ferrite transformation postpones, therefore can not get enough quenching degree
Improve effect.Accordingly, it would be desirable to B content is set to 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 of the austenite after finish rolling postpones.Its result, the rolling set tissue development of hot rolled steel plate,
The intra-face anisotropy of the mechanical property value of the steel plate after annealing becomes big.Thus, drawing and forming easily produces wrinkle (ear),
It addition, out of roundness reduces, during molding, easily cause unfavorable condition.Accordingly, it would be desirable to B content is set to 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%.
Solid solution B amount ratio shared by B content is more than 70%
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 being in solid solution condition in the B contained in steel plate is more than 70%, i.e. the solid solution B in steel plate measures at whole B
When ratio shared in content (B content) is more than 70%, it is possible to obtain the excellent quenching degree wishing in the present invention to realize.Cause
This, be set to more than 70% by ratio shared in B content for solid solution B amount.Solid solution B amount ratio shared by B content is preferably
More than 75%.Should illustrate, solid solution B amount ratio shared by B content refers to { (solid solution B measures (quality %))/(whole B content
(quality %)) } × 100 (%).
Add up to 0.002～0.030% Sb, Sn, Bi, Ge, Te, Se in more than a kind
Sb, Sn, Bi, Ge, Te, Se are the elements with the effect suppressing the nitriding from surface of steel plate, in the present invention, need
In Sb, Sn, Bi, Ge, Te, Se to be contained more than a kind.During it addition, the total of the content of these elements is less than 0.002%, nothing
Method sees enough nitriding inhibitions.Therefore, containing a kind in Sb, Sn, Bi, Ge, Te, Se of adding up to more than 0.002%
Above.The total of the content of Sb, Sn, Bi, Ge, Te, Se is preferably more than 0.005%.On the other hand, though the containing of these elements
Amount total is more than 0.030%, and nitriding inhibition is the most saturated.It addition, these elements have segregation in the trend of crystal boundary, therefore,
If the content of these elements adds up to more than 0.030%, it is likely that cause embrittlement of grain boundaries.Therefore, in the present invention, containing adding up to
It it is more than a kind in Sb, Sn, Bi, Ge, Te, Se of less than 0.030%.The content of Sb, Sn, Bi, Ge, Te, Se preferably adds up to
Less than 0.020%.
As it has been described above, by N content is set to less than 0.0050%, contains simultaneously and add up to 0.002～0.030%
In Sb, Sn, Bi, Ge, Te, Se more than a kind such that it is able to also suppress from steel plate table in the case of annealing in blanket of nitrogen
The nitriding in face, the increase of the nitrogen concentration in suppression steel plate top layer, make from surface of steel plate to the scope along the thickness of slab direction 150 μm degree of depth
The difference of the average nitrogen quantity contained in the average nitrogen quantity being contained within and steel plate entirety is below 30 mass ppm.Suppress as described above
Nitriding, therefore, it is possible to also can make solid solution B amount institute in B content in the steel plate after annealing in the case of annealing in blanket of nitrogen
The ratio accounted for is more than 70%.
If from surface of steel plate to the average nitrogen quantity contained in the range of the μm degree of depth of thickness of slab direction 150 with steel plate entirety
The difference of the average nitrogen quantity contained becomes many more than 30 mass ppm, then be formed at BN, AlN amount of steel plate skin section and be formed at steel
The difference of BN, AlN amount of plate thickness of slab immediate vicinity becomes big.In this case, generation can not get uniform hardness after Quenching Treatment
Etc. unfavorable condition.Accordingly, it would be desirable to by from surface of steel plate to the average nitrogen quantity contained in the range of the μm degree of depth of thickness of slab direction 150 with
The poor suppression of the average nitrogen quantity contained in steel plate entirety is below 30 mass ppm.
Remainder other than the above is Fe and inevitable impurity, but in order to improve quenching degree, Ke Yihan further
There is more than a kind in Ni, Cr, Mo.From the standpoint of obtaining such effect, preferably comprise more than a kind in Ni, Cr, Mo and
The total of its content is set to more than 0.01%.On the other hand, because these element valencys are high, so using 1 in Ni, Cr, Mo
Time kind above, need to make its content adds up to less than 0.50%.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, need to carry out after hot rolling making the annealing (spheroidizing of cementite spheroidizing
Annealing), form the micro-assembly robot being made up of ferrite and cementite.Should illustrate, spheroidizing represents relative to total cementite, length and width
In terms of volume fraction, the state of more than 90% is occupied than the cementite of (major diameter/minor axis)≤3.Especially for making Rockwell hardness with HRB
Be calculated as less than 73 and percentage of total elongation be more than 39%, need the cementite density in ferrite crystal grain is set to 0.08/μm2With
Under.Hereinafter, cementite 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 height, then because of dispersion-strengthened and hardening, percentage elongation can reduce.In order to make hardness be below setting and to make percentage elongation be regulation
More than value, the individual number density by the cementite crystal grain in ferrite crystal grain is needed to be set to 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 about 0.15～1.8 μm with major diameter because be the precipitation strength to steel plate slightly
The size told on, so reducing by the individual number density making the cementite crystal grain in ferrite crystal grain, it is possible to realize intensity
Reduce.The cementite of ferrite grain boundaries is dispersion-strengthened almost without helping, thus by the cementite crystal grain in ferrite crystal grain
Number density is defined as 0.08/μm2Below.Additionally, should illustrate, in addition to above-mentioned ferrite and cementite, unavoidably
Ground generates the remainder tissues such as pearlite, as long as the volume fraction of the total of remainder tissue is less than about 5%, does not damages
The effect of the evil present invention, therefore can also contain this remainder tissue.
The average diameter of total cementite: the cementite average diameter in 0.60 μm～1.00 μm and ferrite crystal grain: 0.40 μ
More than m
Cementite average diameter in ferrite crystal grain is brilliant because of the cementite in ferrite crystal grain less than the steel plate of 0.40 μm
The individual number density of grain increases, so the hardness of the steel plate after Tui Huo rises sometimes.In order to hardness being set to below desired value,
Preferably the cementite average diameter in ferrite crystal grain is set to more than 0.40 μm.Cementite in ferrite crystal grain 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 to make ferrite
The average diameter of the cementite in crystal grain is more than 0.40 μm, need to be set to the average diameter of overall cementite 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, the most sometimes during the heating within image height frequency Quenching Treatment such short time, cementite is not completely dissolved, it is impossible to make hardness become
Below desired value, it is therefore preferable that the average diameter of total cementite is set to below 1.00 μm.Always cementite is average straight
Footpath is more preferably below 0.95 μm.The average diameter of above-mentioned cementite can utilize SEM to observe micro-assembly robot, measures cementite brilliant
The major diameter of grain and minor axis, thus measure the average diameter of the cementite in the average diameter of total cementite and ferrite crystal grain.
Should illustrate, if ferritic particle diameter is the thickest, although then hardness reduces, but the raising of percentage elongation is satisfied sometimes
With, therefore, the ferritic mean diameter in the tissue being made up of above-mentioned ferrite and cementite is preferably below 12 μm, more excellent
Elect below 9 μm as.On the other hand, if ferritic mean diameter is less than 6 μm, steel plate can hardening, therefore ferrum element the most sometimes
The mean diameter of body is preferably more than 6 μm.Above-mentioned ferritic particle diameter can utilize SEM to observe micro-assembly robot and be measured.
3) mechanical property
In the present invention, the automotive parts such as gear class, fluid drive box part, seat harness parts are made to carry out by colding pressing
Molding, it is therefore desirable to excellent processability.In addition, it is necessary to increase hardness by Quenching Treatment, give mar proof to parts.
Therefore, in addition to improving quenching degree, need the hardness of steel plate to be reduced to below HRB73 and increases percentage elongation make percentage of total elongation
(El) it is more than 39%.From the viewpoint of processability, the hardness of steel plate is the lowest more good, but there is also part and quench
Parts, the intensity of raw sheet can affect fatigue properties.Therefore, the hardness of steel plate is preferably greater than HRB60.Additionally, above-mentioned HRB can
To use Rockwell apparatus (B scale) to measure.It addition, percentage of total elongation can use relative to the direction (L that rolling direction is 0 °
Direction) the JIS5 tension test sheet that cuts out, utilize the cupping machine of Shimadzu Seisakusho Ltd. AG10TB AG/XR with 10mm/ minute
Carry out tension test, make the sample of fracture be measured 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: Ar3Transformation temperature～870 DEG C are implemented the hot rollings of finish rolling and are made desired thickness of slab, after finish rolling, with 25 DEG C/s～150 DEG C/
The average cooling rate of s is cooled to 700 DEG C, with coiling temperature: 500 DEG C～700 DEG C are batched, make have pearlite and with
Volume fraction is calculated as the steel plate of the pro-eutectoid ferrite of more than 5%, then at Ac1Spheroidizing is implemented below transformation temperature.Should
Illustrating, 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
It is 0.08/μm to make the individual number density of the cementite crystal grain in ferrite crystal grain after annealing2Hereinafter, need
To have pearlite and be calculated as with volume fraction more than 5% pro-eutectoid ferrite micro-assembly robot hot rolled steel plate implement spheroidizing move back
Fire.Implement after hot roughing in the hot rolling of finish rolling, if final rolling temperature uprises, then the ratio of pro-eutectoid ferrite more than 870 DEG C
Example diminishes, and can not get the individual number density of the cementite crystal grain of regulation after spheroidizing.It 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, is preferably set to less than 850 DEG C by final rolling temperature.On the other hand, if final rolling temperature is less than Ar3Transformation temperature,
Forming thick ferrite crystal grain with after annealing the most after hot rolling, percentage elongation significantly reduces.Therefore, final rolling temperature is set to Ar3
More than transformation temperature.Final rolling temperature is preferably more than 820 DEG C.Should illustrate, using the surface temperature of steel plate as final rolling temperature.
Average cooling rate from final rolling temperature to 700 DEG C: 25 DEG C/s～150 DEG C/s
It is 0.08/μm to make the individual number density of the cementite crystal grain in ferrite crystal grain after annealing2Hereinafter, need
To have pearlite and be calculated as with volume fraction more than 5% pro-eutectoid ferrite micro-assembly robot hot rolled steel plate implement spheroidizing move back
Fire.After finish rolling in hot rolling, the temperature province to 700 DEG C is equivalent to exist the temperature of ferrite and pearlite starting temperature of transformation
Region, therefore to make a point rate for the pro-eutectoid ferrite in the steel plate after hot rolling be calculated as more than 5% with volume fraction, from finish rolling temperature
The rate of cooling of degree to 700 DEG C becomes key factor.It is less than from the average cooling rate of the temperature province of final rolling temperature to 700 DEG C
During 25 DEG C/s, ferrite transformation is difficult to carry out at short notice, and pearlite point rate uprises more than necessity, therefore can not get with body
Long-pending rate is calculated as the pro-eutectoid ferrite of more than 5%.It addition, because generating thick pearlite, so difficult after spheroidizing
To obtain desired steel plate tissue.Therefore, the average cooling rate of temperature province to 700 DEG C after finish rolling is set to 25
DEG C/more than s.It addition, in order to obtain 0.07/μm2The cementite grain of the ferrite intragranular after following spheroidizing
Number density, is preferably set to point rate of pro-eutectoid ferrite more than 10% in terms of volume fraction, now, this preferably averagely cools down speed
Degree is set to 30 DEG C/more than s.This average cooling rate is more preferably 40 DEG C/more than s.On the other hand, if this average cooling rate
More than 150 DEG C/s, then it is difficult to obtain pro-eutectoid ferrite, therefore average cooling rate to 700 DEG C after finish rolling is set to 150
DEG C/below s.This average cooling rate is preferably 120 DEG C/below s.This average cooling rate is more preferably 100 DEG C/below s.This
Outward, using the surface temperature of steel plate as this temperature.
Coiling temperature: 500 DEG C～700 DEG C
After steel plate after finish rolling states cooling on the implementation, coil into steel ring shape with the coiling temperature of 500 DEG C～700 DEG C.
If coiling temperature is more than 700 DEG C, the most not only the tissue coarsening of hot rolled steel plate and desired steel cannot be obtained after annealing
Plate tissue, and the intensity of steel plate is too low, when coiling into steel ring shape, sometimes deforms because of the deadweight of steel ring, therefore behaviour
On work the most preferred.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, and percentage elongation diminishes 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 the steel plate after hot rolling: there is pearlite and be calculated as the pro-eutectoid ferrite of more than 5% with volume fraction
Tissue
In the present invention, after spheroidizing described later, obtain having be made up of ferrite and cementite and above-mentioned ferrum element
The individual number density of the 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 impact of the micro-assembly robot of the steel plate after hot rolling is big.Become by the micro-assembly robot of the steel plate after making hot rolling and there is pearly-lustre
Body and be calculated as with volume fraction more than 5% the tissue of pro-eutectoid ferrite, it is possible to after spheroidizing, become desired group
Knit, be accordingly changed into the steel that processability is high.It addition, if not there is point rate of pearlite or pro-eutectoid ferrite with volume fraction
The meter steel plate less than 5%, then at Ac1After carrying out spheroidizing below transformation temperature, can not get regulation cementite crystal grain
Number density, armor plate strength uprises.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 have pearlite and be calculated as the tissue of pro-eutectoid ferrite of more than 5% with volume fraction.Preferably become by pearl
Body of light and be calculated as the tissue that the pro-eutectoid ferrite of more than 10% is constituted with volume fraction.Should illustrate, in order to obtain after annealing
Uniform tissue, a point rate for pro-eutectoid ferrite is preferably calculated as less than 50% with volume fraction.
Annealing temperature: Ac1Below transformation temperature
As above the hot rolled steel plate obtained is implemented annealing (spheroidizing).If annealing temperature is more than Ac1Transformation temperature, then
Austenite separates out, and forms thick pearlitic structrure, become uneven tissue in cooling procedure after annealing.Therefore, will
Annealing temperature is set to Ac1Below transformation temperature.Should illustrate, lower limit does not has a special provision, but the carburizing in making ferrite crystal grain
From the standpoint of the individual number density of body crystal grain becomes desired value, annealing temperature is preferably more than 600 DEG C, and more preferably 700
More than DEG C.Should illustrate, atmosphere gas can use any one in the mixed gas of nitrogen, hydrogen, nitrogen and hydrogen, and these are preferably used
Gas but it also may use Ar, be not particularly limited.It addition, annealing time is preferably 0.5～40 hour.During by annealing
Between be set to more than 0.5 hour, it is possible to stably obtain destination organization, the hardness of steel plate can be set to below setting, will stretch
Long rate is set to more than setting, and therefore annealing time is preferably more than 0.5 hour.More preferably more than 8 hours.It addition,
If annealing time was more than 40 hours, then production rate reduces, and manufacturing cost easily becomes excessive, and therefore annealing time is preferably 40
Below hour.Should illustrate, using annealing temperature as the surface temperature of steel plate.It addition, using annealing time as maintenance regulation
The time of temperature.
Should illustrate, for the high-carbon steel of the melting present invention, converter, electric furnace can use.It addition, so melting forms
High-carbon steel by ingot casting-split rolling method or continuously casting and make blanket.Blanket the most after the heating, carries out hot rolling.Should say
Bright, in the case of by the blanket that continuously casting manufactures, can apply and directly roll, change directly to roll and directly carry out rolling or for suppression
Temperature reduce purpose and roll after thermal protection.During it addition, heating blanket carries out hot rolling, in order to avoid the table caused by scale
The variation of surface state, is preferably set to less than 1280 DEG C by blanket heating-up temperature.For hot rolling, in order to carry out essence with the temperature of regulation
Roll, the heater meanses such as plate heater can be utilized in hot rolling to carry out the heating of material to be rolled.
Embodiment 1
The steel forming the chemical composition with steel numbering system A～J shown in table 1 carries out melting, then with the heat shown in table 2
After kicker part carries out finish rolling, carry out cooling down, batching, make hot rolled steel plate.Should illustrate, the rate of cooling shown in table 2 is from essence
To the average cooling rate of 700 DEG C after rolling.Then, pickling is carried out, with the annealing conditions shown in table 2, at blanket of nitrogen (atmosphere gas
Body: nitrogen) middle enforcement annealing (spheroidizing), manufacture thickness of slab 4.0mm, the hot rolled steel plate (hot-roll annealing plate) of plate width 1000mm.
To the hot-roll annealing plate so manufactured, investigate hardness, percentage elongation, micro-assembly robot.It addition, also to the micro-group of hot rolled steel plate before annealing
Knit and investigate.Show the result in table 2.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 taked by the plate width central part of the steel plate after annealing, uses Rockwell apparatus (B scale) to measure 5 points, obtains
Meansigma methods.
The percentage of total elongation (El) of hot-roll annealing plate
Use the steel plate after annealing in the JIS5 tension test cut out with the direction (L direction) that rolling direction is 0 °
Sheet, utilizes the cupping machine of Shimadzu Seisakusho Ltd. AG10TB AG/XR to carry out tension test with 10mm/ minute, by the sample of fracture
Percentage elongation (percentage of total elongation) is obtained to fetching.
Micro-assembly robot
The micro-assembly robot (micro-assembly robot of hot rolled plate) of the hot rolled steel plate before annealing is observed by SEM, obtains the kind of its tissue
Class and point rate of pro-eutectoid ferrite.Rate is divided, by being divided into ferrite area and ferrite area for pro-eutectoid ferrite
Position in addition, obtains the ratio of ferrite area and obtains area occupation ratio, using this value as the volume fraction of pro-eutectoid ferrite.Should
Give explanation, in the hot rolled steel plate before the annealing shown in table 2, above-mentioned SEM observe and confirm to there is pearlite.
For the micro-assembly robot (micro-assembly robot of hot-roll annealing plate) of the steel plate after annealing, the sample will taked from plate width central part
Cut off after grinding, implement nital (nital) corrosion, use sweep electron microscope, utilize 1/4 at thickness of slab
The macrograph of the multiplying power shooting of 3000 times is sentenced in 5 put, and observes the kind of its tissue, and measure non-existent on crystal boundary,
Major diameter is the number of the cementite of more than 0.15 μm, by this number divided by the area of the visual field of photo, obtains in ferrite crystal grain
Cementite density (the individual number density of cementite crystal grain).For cementite diameter, above-mentioned macrograph is used to measure each carburizing
The major diameter of body crystal grain and minor axis, obtain the average diameter of cementite in whole cementites and crystal grain.For ferritic grain
Footpath, uses above-mentioned macrograph to obtain grain size number, calculates average crystallite particle diameter.
It addition, for the steel plate (hot-roll annealing plate) after annealing, obtain as follows in average N amount and the steel plate of top layer 150 μm
The difference of average N amount, the ratio that solid solution B amount is shared in B content.Show the result in table 2.
The average N amount of top layer 150 μm is the difference of average N amount with steel plate
Use the sample that the plate width central part of the steel plate after annealing is taked, measure average N amount and the steel plate of top layer 150 μm
In average N amount, obtain the difference of the average N amount of top layer 150 μm and the average N amount in steel plate.Should illustrate, here top layer 150 μm
Average N amount refer to, from surface of steel plate to along thickness of slab direction be contain in the range of the 150 μm degree of depth N amount.It addition, ask as follows
Go out the average N amount of top layer 150 μm.That is, the surface from the steel plate taked starts cutting, by steel plate from surface cut to 150 μm
The degree of depth, takes the cutting blade now produced as sample.Measure the N amount as top layer 150 μm of the N amount in this sample.Top layer 150
In the average N amount of μm and steel plate, average N amount utilizes non-active gas melting-thermal conductivity method to measure and obtain.So long as obtain
The average N amount (surface～the N from surface to the scope of the 150 μm degree of depth measure) of top layer 150 μm is measured (in steel with the average N steel plate
N content) difference be below 30 mass ppm, then can be evaluated as suppressing nitriding.
The ratio that solid solution B amount is shared in B content
Sample taked by the plate width central part of the steel plate after annealing.With 10 volume %Br methanol, the BN in steel is extracted
Taking, the whole B content from steel deduct the B content separated out with the form of BN, obtain solid solution B amount.By { (solid solution B measures (matter
Amount %))/(whole B content (quality %)) } × 100 (%) obtain in solid solution B whole B content (B content) of containing in steel of amount
Shared ratio.As long as this ratio is more than 70 (%), then can be evaluated as the reduction that solid solution B can be suppressed to measure.
Steel plate hardness (quenching hardness) after quenching
Using the steel plate after annealing as raw sheet, 3 kinds of Quenching Treatment of following enforcement, the steel plate hardness (quenching after investigation quenching
Hardness), evaluate quenching degree.Show the result in table 2.
Treadmill test sheet (width 15mm × length 40mm × plate taked by the plate width central part of the steel plate (raw sheet) after annealing
Thick 4mm), use above-mentioned treadmill test sheet, utilize and keep 30s to carry out the method (water-cooled) of water-cooled immediately, 870 at 870 DEG C
The method (120 DEG C of oil are cold) carrying out cooling down with the oil of 120 DEG C immediately after keeping 30s at DEG C carries out Quenching Treatment.Through hardening characteristic
It is the section to the test film after Quenching Treatment, utilizes Vickers pyramid hardness testing machine to measure under conditions of load 1kgf firmly at 5
Spend and obtain average hardness, and be averaged hardness as quenching hardness.
Additionally, disc test sheet taked by the plate width central part of the steel plate (raw sheet) after annealingHigh-frequency quenching is utilized (to heat with 200 DEG C/s of firing rate, after reaching 1000 DEG C
Carry out water-cooled) implement Quenching Treatment.Now, the section of the test film of test film outermost perimembranous is utilized Vickers pyramid hardness testing machine
Under conditions of load 0.2kgf, measure 2 point hardnesses obtain average hardness, be averaged hardness as quenching hardness.
30s is kept to carry out water-cooled and carry out the cold quenching hardness of oil at 120 DEG C and be satisfied by the condition of table 3 at 870 DEG C
In water-cooled after hardness, 120 DEG C of cold rear hardness of oil, and the quenching hardness after high-frequency quenching is met the high-frequency quenching hardness of table 3
Situation be judged to qualified (zero), be evaluated as quenching degree excellent.It addition, keep after 30s water-cooled at 870 DEG C and at 120 DEG C
When carrying out the condition that any one in the hardness after the cold hardness of oil and high-frequency quenching water-cooled is unsatisfactory for shown in table 3, it is set to not conform to
Lattice (×), it is evaluated as quenching degree poor.Should illustrate, table 3 represents and can empirically be evaluated as quenching degree sufficiently and 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 and be made up of ferrite and cementite and above-mentioned ferrum element
Cementite density in body crystal grain is 0.08/μm2Following micro-assembly robot, hardness is 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 the most excellent.
Table 3
Claims (5)
1. a high-carbon hot-rolled steel sheet, it has following composition, i.e. contains in terms of quality %: C:0.20～0.40%, Si:
Less than 0.10%, below Mn:0.50%, below P:0.03%, below S:0.010%, solid solution aluminum: less than 0.10%, N:
Less than 0.0050%, B:0.0005～0.0050%, contain further add up to 0.002～the Sb of 0.030%, Sn, Bi, Ge,
In Te, Se more than a kind, remainder is Fe and inevitable impurity, and solid solution B amount ratio shared by B content is
More than 70%, and, have be made up of ferrite and cementite and cementite density in described ferrite crystal grain be 0.08/
μm2Following micro-assembly robot, hardness is calculated as less than 73 with HRB, and percentage of total elongation is more than 39%.
High-carbon hot-rolled steel sheet the most 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.
High-carbon hot-rolled steel sheet the most according to claim 1 and 2, wherein, the tissue being made up of described ferrite and cementite
In the average diameter of total cementite be 0.60 μm～1.00 μm, the cementite average diameter in ferrite crystal grain be 0.40 μm with
On.
4. a manufacture method for high-carbon hot-rolled steel sheet, after having the following hot roughing of steel formed, with final rolling temperature as Ar3Phase
Height～870 DEG C carry out finish rolling, are cooled to 700 DEG C with the average cooling rate of 25 DEG C/s～150 DEG C/s, with coiling temperature are
500 DEG C～700 DEG C batched, and thus makes and has pearlite and be calculated as the pro-eutectoid ferrite of more than 5% with volume fraction
Steel plate, then, by this steel plate at Ac1Annealing below transformation temperature, wherein, consisting of of described steel contains in terms of quality %:
C:0.20～0.40%, below Si:0.10%, below Mn:0.50%, below P:0.03%, below S:0.010%, solid solution aluminum:
Less than 0.10%, below N:0.0050%, B:0.0005～0.0050%, contains further and adds up to 0.002～0.030%
In Sb, Sn, Bi, Ge, Te, Se more than a kind, remainder is Fe and inevitable impurity.
The manufacture method of high-carbon hot-rolled steel sheet the most according to claim 4, wherein, described steel contains further in terms of quality %
There is more than a kind in Ni, Cr, Mo of adding up to less than 0.50%.
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| CN110325657A (en) * | 2017-02-21 | 2019-10-11 | 杰富意钢铁株式会社 | High-carbon hot-rolled steel sheet and its manufacturing method |
| CN111655893A (en) * | 2018-01-30 | 2020-09-11 | 杰富意钢铁株式会社 | High carbon hot-rolled steel sheet and method for producing same |
| CN113366137A (en) * | 2019-01-30 | 2021-09-07 | 杰富意钢铁株式会社 | High carbon hot-rolled steel sheet and method for producing same |
| CN113366136A (en) * | 2019-01-30 | 2021-09-07 | 杰富意钢铁株式会社 | High carbon hot-rolled steel sheet and method for producing same |
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| US12110568B2 (en) * | 2019-02-28 | 2024-10-08 | Jfe Steel Corporation | Steel sheet and member, and methods for manufacturing same |
| JP7067578B2 (en) * | 2019-02-28 | 2022-05-16 | Ｊｆｅスチール株式会社 | Manufacturing method of steel plate and steel plate and members |
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| CN111655893B (en) * | 2018-01-30 | 2022-05-03 | 杰富意钢铁株式会社 | High carbon hot-rolled steel sheet and method for producing same |
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| CN113366136A (en) * | 2019-01-30 | 2021-09-07 | 杰富意钢铁株式会社 | High carbon hot-rolled steel sheet and method for producing same |
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Also Published As
| Publication number | Publication date |
|---|---|
| TWI557239B (en) | 2016-11-11 |
| EP3091098A4 (en) | 2017-04-05 |
| KR20160138230A (en) | 2016-12-02 |
| JPWO2015146173A1 (en) | 2017-04-13 |
| CN106133170B (en) | 2017-12-26 |
| EP3091098A1 (en) | 2016-11-09 |
| JP6065120B2 (en) | 2017-01-25 |
| WO2015146173A1 (en) | 2015-10-01 |
| TW201538744A (en) | 2015-10-16 |
| KR101892524B1 (en) | 2018-08-28 |
| EP3091098B1 (en) | 2018-07-11 |
| US20170121787A1 (en) | 2017-05-04 |
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