CN105026596A - Hot-rolled steel sheet having excellent drawability and post-processing surface hardness - Google Patents
Hot-rolled steel sheet having excellent drawability and post-processing surface hardness Download PDFInfo
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- CN105026596A CN105026596A CN201480011947.0A CN201480011947A CN105026596A CN 105026596 A CN105026596 A CN 105026596A CN 201480011947 A CN201480011947 A CN 201480011947A CN 105026596 A CN105026596 A CN 105026596A
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/06—Surface hardening
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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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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
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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
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- 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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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- 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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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- 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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- 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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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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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Abstract
A hot-rolled steel sheet having a sheet thickness of 2 to 15 mm and having a component composition, by mass, of 0.3% or less of C, 0.5% or less of Si, 0.2 to 1% of Mn, 0.05% or less of P, 0.05% or less of S, 0.01 to 0.1% of Al, and 0.008 to 0.025% of N, with the remainder made up by iron and unavoidable impurities, the solid-solution N being at least 0.007%. In ferrite crystal grains located at the position of depth t/4 (where t is the thickness of the hot-rolled steel sheet), the area ratio of crystal grains within a plane orientation of 10 degrees from the (123) plane is at least 20%, the area ratio of crystal grains within a plane orientation of 10o from the (111) plane is at least 5%, the area ratio of crystal grains within a plane orientation of 10o from the (001) plane is no more than 20%, and the average grain diameter of ferrite crystal grains located at the position of depth t/4 is 3 to 35 mu m.
Description
Technical field
The present invention relates to both work in-processes and demonstrate good drawing processibility, demonstrate again the hot-rolled steel sheet of set surface hardness after processing.
Background technology
In recent years, from the view point of environment protection, rise to object with the fuel efficiency of automobile, the various parts of automobile, such as, to the lightweight of the steel of the transmission mechanism part and housing etc. for gear etc., namely surging all the more with the requirement of high strength.In order to comply with the requirement of such lightweight high-intensity, as the general steel used, the steel (forge hot material) bar steel having been carried out forge hot can be used.In addition, in order to cut down the CO in part manufacturing process
2quantity discharged, up to now, the cold forging about the part of the gear processed through forge hot etc. requires also surging.
So, cold working (cold forging), processes with hot-work and temperature and compares, have productivity high, and the sharp point that the yield rate of dimensional precision and steel is all good.But during by such cold working finished parts, structure is debatable, the intensity in order to the part by cold working is guaranteed more than expected preset value, must need working strength, the steel that namely resistance to deformation is high., the resistance to deformation of the steel used is higher, more can cause the lost of life of cold working metal die, and has the difficult point that crackle easily occurs during cold working.
Therefore, the method always implemented is, being become by steel cold forging both after shaped, carries out the thermal treatment of Q-tempering etc., thus manufactures the high strength part guaranteed in set intensity (hardness).But the thermal treatment after cold forging, accessory size will inevitably change, and therefore just need Secondary mechanical workout of to cut etc. to be revised, this just expects a kind of solve scheme that can omit thermal treatment and subsequent processing.
In order to solve above-mentioned problem, such as, disclose and utilize solid solution C in soft steel, suppress the carrying out of room temperature ageing, use strain aging and guarantee set age hardening amount, thus obtain the cold forging wire rod bar steel (with reference to patent documentation 1) of excellent in distortion aging property.
But this technology only measures controlled strain timeliness by solid solution C, and the steel that the required hardness strength after obtaining sufficient cold-workability and processing is existed side by side are had any problem.
Therefore, the applicant, be conceived to solid solution C contained by steel and solid solution N to the difference of the impact that resistance to deformation and static strain timeliness cause, carry out various research, it found that, by suitably controlling the amount of these solid solution elements, then can obtain both work in-processes and play good cold-workability, after cold working (cold forging), demonstrate again the physical structure steel of set surface hardness (intensity), and carry out patent application (with reference to patent documentation 2).
Existing side by side of high rigidity (high strength) after these steel achieve cold-workability and processing, but same with the wire rod bar steel described in above-mentioned patent documentation 1, and it is forge hot material, has the difficult point that manufacturing cost is high.Therefore, in order to make manufacturing cost more cost degradation, replacing existing forge hot material, also being studied with the technology that hot-rolled steel sheet makes automobile part by cold working.
Such as, propose there is one after nitriding treatment, the hot-rolled steel sheet (with reference to patent documentation 3) of the nitriding treatment of high surface hardness and sufficient hardening depth can be obtained.
But this technology needs to carry out nitriding treatment again after cold working, has the problem that can not realize sufficient cost degradation.
In addition, also propose there is a kind of hot-rolled steel sheet, it consists of, containing below C:0.10%, Si: lower than 0.01%, below Mn:1.5% and below Al:0.20%, and contain in the scope of (Ti+Nb)/2:0.05 ~ 0.50%, with below S:0.005%, below N:0.005%, below O:0.004%, S, the mode being aggregated in less than 0.0100% of N and O contains above element, and make microstructure be the ferrite single phase structure of the essence of more than 95%, this hot-rolled steel sheet, the dimensional precision of precision punching machined surface is excellent, and the surface hardness of the punch side after processing is high, in addition resistance to red rust defective also excellent (with reference to patent documentation 4).
But, this hot-rolled steel sheet, N is that harmful element is limited in extremely low content, with the hot-rolled steel sheet of the present application utilizing N energetically, completely different inwardly in technology.
In general, about in order to the mutually set organizational controls that the plasticity improving steel plate is carried out than ever, for the steel-sheet deep drawing processibility of the body panel of automobile, plastic anisotropy's (r value (Lankford value): the ratio that the wide strain of the plate in tension test and thickness of slab strain) of material is larger, its processibility is higher, in this external recrystallize set tissue, make to be parallel to plate planar orientation { 111} face is very flourishing, weaken { 100} planar orientation, for deep drawability raising integral, this point is experimentally or be in theory all confirmed (with reference to non-patent literature 1).
Therefore, the effort that all set organizational controls by steel plate improve processibility has been carried out.
Such as, proposition has a kind of high-strength steel sheet, it in mass %, containing C:0.01 ~ 0.1%, Si:0.01 ~ 2%, Mn:0.05 ~ 3%, P≤0.1%, S≤0.03%, Al:0.005 ~ 2.0%, N≤0.01%, B:0.0005 ~ 0.0030, containing Ti in the scope of this external satisfaction Ti-(48/12) C-(48/14) N-(48/32) S >=-0.03%, surplus is made up of Fe and inevitable impurity, wherein, be less than 0.2 by the deviation of the hardness of this steel plate divided by the value of its mean value, and, rolling direction { the face intensity in 110} face is less than 1.7, punching hole expandability excellence (with reference to patent documentation 5).
In addition, proposition has a kind of high tensile steel plate, it in mass %, containing C: higher than 0.0005% and lower than 0.10%, below Si:1.5%, more than Mn:0.1% below 3.0%, below P:0.080%, below S:0.03%, more than sol.Al:0.01% below 0.50% and below N:0.005%, and containing among below Nb:0.20% and below Ti:0.20% selection one or both, surplus was made up of Fe and forming of inevitable impurity, about structure of steel, in volume fraction more than 60% for ferritic phase, with the density function of three-dimensional crystals orientation (ODF) { φ 1, Φ, φ 2} counts, Φ is 0 °, φ 1 is 0 °, ODF{0 ° when φ 2 is 45 °, 0 °, 45 ° } intensity below 3.0, and Φ is 35 °, φ 1 is 0 °, ODF{0 ° when φ 2 is 45 °, 35 °, 45 ° } intensity be more than 2.5, the scope of less than 4.5, cracking is difficult to when can be provided in extrusion molding, and the high tensile steel plate that the anisotropy of ductility is little (with reference to patent documentation 6).
Proposition has a kind of hot-rolled steel sheet, it has following composition, namely in mass %, containing C:0.01 ~ 0.05%, below Si:0.2%, below Mn:0.50%, Al:0.005 ~ 0.10%, below P:0.05%, below S:0.05%, below N:0.01%, below O:0.01%, surplus is made up of Fe and inevitable impurity, and it has as undertissue, namely average crystal grain diameter is that the ferritic phase of 40 ~ 60 μm is single-phase, and, { 118} < 110 > is with { the random strength ratio of 115} < 110 > is respectively more than 10, { 111} < 110 > is with { the random strength ratio of 111} < 121 > is respectively 1 with undertissue, the hot-rolled steel sheet that intra-face anisotropy after cold rolling-recrystallization annealing is little (with reference to patent documentation 7) can be provided.
As above example, the plasticity of attempting steel plate by set organizational controls improve carried out all, outside plate, body framing material, the chassis part of what major part related to is automobile.In the present invention as in the transmission mechanism part of the gear etc. of object and housing etc., required plasticity is different from Automobile body parts, is not only to require drawing processibility and pultrusion processibility etc., also requires the part of the surface hardness after processing as described so.
In addition, in the field of transmission mechanism part, from the forged article of bar steel, () such as forge hot, cold forging, the research of the part manufacture undertaken by steel plate for target with the lightweight of part, cost degradation is also being carried out, and requires further plasticity.
[look-ahead technique document]
[patent documentation]
The flat 10-306345 publication of [patent documentation 1] Japanese Laid-Open
[patent documentation 2] Japanese Laid-Open 2009-228125 publication
[patent documentation 3] Japanese Laid-Open 2007-162138 publication
[patent documentation 4] Japanese Laid-Open 2004-137607 publication
[patent documentation 5] Japanese Laid-Open 2009-24226 publication
[patent documentation 6] Japanese Laid-Open 2012-158797 publication
[patent documentation 7] Japanese Laid-Open 2007-291514 publication
[non-patent literature]
[non-patent literature 1] Nippon Steel association: " forefront that recrystallize set tissue and the application recrystallize towards this organizational controls are studied ", in March, 1999, p.208
Summary of the invention
The present invention is conceived to above-mentioned situation and is formed, and its object is to, provides a kind of both work in-processes to demonstrate good drawing processibility, demonstrate again the hot-rolled steel sheet of set surface hardness after processing.
First invention, is the hot-rolled steel sheet of drawing processibility and the surface hardness excellence after processing, it is characterized in that,
Thickness of slab is 2 ~ 15mm,
Composition consists of,
Be in mass % (following, relate to chemical composition all with.)，
Below C:0.3% (not containing 0%),
Below Si:0.5% (not containing 0%),
Mn：0.2～1％、
Below P:0.05% (not containing 0%),
Below S:0.05% (not containing 0%),
Al：0.01～0.1％、
N：0.008～0.025％，
Surplus by iron and inevitable impurity,
More than solid solution N:0.007%,
About be present in degree of depth t/4 (t: thickness of slab, lower with.) the ferrite crystal grain of position,
The area occupation ratio of the ferrite crystal grain of relative (123) face of plate planar orientation within 10 ° is more than 20%,
The area occupation ratio of the ferrite crystal grain of relative (111) face of plate planar orientation within 10 ° is more than 5%,
The area occupation ratio of the ferrite crystal grain of relative (001) face of plate planar orientation within 10 ° is less than 20%,
Further, the median size being present in the ferrite crystal grain of the position of described degree of depth t/4 is 3 ~ 35 μm.
Second invention is the steel plate according to the first invention, wherein,
Become to be grouped into also containing below Cr:2% (not containing 0%) and/or below Mo:2% (not containing 0%).
3rd invention is according to the first or two hot-rolled steel sheet described in invention, wherein,
Become be grouped into also containing from
Below Ti:0.2% (not containing 0%),
Below Nb:0.2% (not containing 0%),
At least one selected in the group that below V:0.2% (not containing 0%) is formed.
4th invention is the hot-rolled steel sheet according to any one of the first ~ tri-invention, wherein,
Become to be grouped into also containing below B:0.005% (not containing 0%).
5th invention is the hot-rolled steel sheet according to any one of the first ~ tetra-invention, wherein,
Become be grouped into also containing from
Below Cu:5% (not containing 0%),
Below Ni:5% (not containing 0%),
At least one selected in the group that below Co:5% (not containing 0%) is formed.
6th invention is the hot-rolled steel sheet according to any one of the first ~ five invention, wherein,
Become be grouped into also containing from
Below Ca:0.05% (not containing 0%),
Below REM:0.05% (not containing 0%),
Below Mg:0.02% (not containing 0%),
Below Li:0.02% (not containing 0%),
Below Pb:0.5% (not containing 0%),
At least one selected in the group that below Bi:0.5% (not containing 0%) is formed.
According to the present invention, in the tissue of ferrite body with set median size, by guaranteeing that solid solution N measures, and be set tissue morphology by the set organizational controls of hot-rolled steel sheet, even if in the part requiring drawing processibility, by improving the deformability in processing, the life-span of metal die still can be extended still, and steel plate can be provided to be difficult to crackle occurs, and the part obtained after processing can guarantee the hot-rolled steel sheet of set surface hardness.
Embodiment
Below, for hot-rolled steel sheet of the present invention (hereinafter also referred to as " steel plate of the present invention " or be only called " steel plate ".), be illustrated in more detail.Steel plate of the present invention, with the forge hot material described in above-mentioned patent documentation 2, is guaranteeing in N solid solution capacity this point common, but is improving cutoff range in permission C content, control the set tissue morphology of steel plate, and make the aspect of ferrite crystal grain miniaturization different.
(thickness of slab of steel plate of the present invention: 2 ~ 15mm)
First, steel plate of the present invention, with the steel plate of thickness of slab 2 ~ 15mm for object.When thickness of slab is lower than 2mm, the rigidity as structure can not be guaranteed.On the other hand, if thickness of slab is higher than 15mm, be then difficult to reach the set tissue morphology specified in the present invention, the drawing processibility that can not get expecting improves effect.Preferred thickness of slab is 3 ~ 14mm.
Next, be grouped into for the one-tenth forming steel plate of the present invention and be described.Below, the unit of chemical composition is all quality %.
(one-tenth of steel plate of the present invention is grouped into)
Below < C:0.3% (not containing 0%) >
C is the element formation of the tissue of steel plate being caused to tremendous influence, although tissue is ferrite body tissue, or ferrite-pearlite heterogeneous structure, in order to become the least possible ferrite body tissue of perlite, it is the element needing limited content.If make C contain superfluously, then the perlite in steel plate tissue divides rate to rise, and due to pearlitic work hardening, likely causes resistance to deformation excessive.Therefore, the C content in steel plate is limited in less than 0.3%, preferably below 0.25%, more preferably below 0.2%, particularly preferably in less than 0.15%.But if the content of C is very few, then the deoxidation in the melting of steel becomes difficulty, and be difficult to intensity, surface hardness after meeting deep drawing processing, be therefore preferably more than 0.0005%, be more preferably more than 0.0008%, be particularly preferably more than 0.001%.
Below < Si:0.5% (not containing 0%) >
Si makes the resistance to deformation of steel plate increase by solid solution in steel, is therefore the element needing to do one's utmost to reduce.For this reason, the Si content in steel plate, in order to suppress the increase of resistance to deformation to be limited in less than 0.5%, preferably below 0.45%, more preferably below 0.4%, particularly preferably in less than 0.3%.But, if the content of Si is few, then the deoxidation difficulty in melting, and be difficult to intensity, surface hardness after meeting deep drawing processing, be therefore preferably more than 0.005%, be more preferably more than 0.008%, be particularly preferably more than 0.01%.
＜Mn：0.2～1％＞
Mn is the element at steelmaking process with the effect of deoxidation and desulfurization.When improving the content of the N in steel in addition, due to the dynamic strain aging that the heating in processing causes, cause crackle easily to occur, but then, processibility when at this moment Mn makes improves, and has the effect suppressing crackle.In order to effectively play these effects, the Mn content in steel is more than 0.2%, is preferably more than 0.22%, is more preferably more than 0.25%.But if Mn content is superfluous, then resistance to deformation is excessive, the ununiformity of the tissue caused because of segregation occurs, and is therefore less than 1%, is preferably less than 0.98%, is more preferably less than 0.95%.
Below < P:0.05% (not containing 0%) >
P is inevitably by the impurity element contained in steel, if but its contained in ferrite, then make cold-workability deterioration at ferrite grain boundary segregation, in addition, it makes higher content strengthen, is the element of reason forming resistance to deformation increase.Therefore, the content of P, from the view point of cold-workability, preferably do one's utmost to reduce, but extreme minimizing can cause the increase of steel-making cost, therefore considers process capability and is less than 0.05%, be preferably less than 0.03%.
Below < S:0.05% (not containing 0%) >
S is also same with P, is inevitable impurity, as FeS at crystal grain boundary with membranaceous precipitation, be the element making processibility deterioration.In addition, also have and cause hot short effect.Therefore, from the view point of raising deformability, in the present invention, make S content be less than 0.05%, be preferably less than 0.03%.But, make S content reach 0 and industrially have any problem.Further, S has the effect that machinability is improved, and therefore improves from the view point of machinability, recommends preferably to make it containing more than 0.002%, more preferably containing more than 0.006%.
＜Al：0.01～0.1％＞
Al is to the effective element of deoxidation in steelmaking process.In order to obtain the effect of this deoxidation, the Al content in steel is more than 0.01%, is preferably more than 0.015%, is more preferably more than 0.02%.But if the content of Al is superfluous, then make toughness reduce, crackle easily occurs, and is therefore less than 0.1%, be preferably less than 0.09%, be more preferably less than 0.08%.
＜N：0.008～0.025％＞
N, by under the static strain timeliness after processing, is the important element for obtaining set intensity.Therefore, the N content in steel is more than 0.008%, is preferably more than 0.0085%, is more preferably more than 0.009%.But if the content of N is superfluous, then except static strain timeliness, the impact of the dynamic strain aging in processing is also remarkable, and resistance to deformation increase is not suitable for, and is therefore less than 0.025%, is preferably less than 0.023%, is more preferably less than 0.02%.
The above > of < solid solution N:0.007%
And, by guaranteeing that in steel plate given amount is (hereinafter referred to as " solid solution N measures ".) solid solution N, can less make resistance to deformation improve, and promote static strain timeliness.In order to ensure intensity required after cold working, solid solution N amount needs to be more than 0.007%.But if solid solution N measures superfluous, then cold-workability deterioration, is therefore preferably less than 0.03%.Further, the content of the N in steel is less than 0.025%, and therefore solid solution N amount does not reach more than 0.025% in fact.
At this, solid solution N of the present invention measures, and is according to JIS G 1228, deducts N total amount of compound and the amount of trying to achieve from the total N content steel.Below illustrate the method for masurement of the practicality that this solid solution N measures.
(a) Inert Gas Fusion Method-thermal conductivity method (measurement of total N content)
Put into crucible by from the sample cut for examination material, melt in inert gas flow and extract N, extractives be transported to thermal conductivity cell and measure the change of thermal conductance, trying to achieve total N content.
(b) ammonia fractionation by distillation indophenol blue absorption photometry (measurement of N total amount of compound)
By from the sample cut for examination material, dissolve in 10%AA system electrolytic solution, carry out constant-current electrolysis, measure the N total amount of compound in steel.The 10%AA system electrolytic solution used, being the electrolytic solution of the non-aqueous solvent be made up of 10% acetone, 10% tetramethylammonium chloride, surplus methyl alcohol, is the solution that can not make steel Surface Creation passive state epithelium.
Make the sample for examination material be about 0.5g, dissolve in this 10%AA system electrolytic solution, with the strainer of the polycarbonate of hole dimension 0.1 μm, filter the undissolved residue (N compound) generated.By the undissolved residue obtained, thermal degradation in sulfuric acid, potassium sulfate and pure copper chip, makes resolvent and filtrate be combined.After making this solution alkaline with sodium hydroxide, carry out wet distillation, absorb the ammonia distillated with dilute sulphuric acid.Add that phenol ferments again, clorox and pentacyano nitroso-group iron (III) sour sodium (ペ Application タ シ ア ノ ニ ト ロ シ Le iron (III) sour Na ト リ ウ system) and generate blue complex, use absorption spectrophotometry to measure absorbancy, try to achieve N total amount of compound.
Then, from the total N content that the method by above-mentioned (a) is tried to achieve, deduct the N total amount of compound of being tried to achieve by the method for above-mentioned (b), then can try to achieve solid solution N and measure.
Base steel of the present invention is originally containing mentioned component, and surplus is iron and inevitable impurity, but in addition, in the scope not damaging effect of the present invention, can also add following permission composition.
Below < Cr:2% (not containing 0%) and/or below Mo:2% (not containing 0%) >
Cr improves the intensity of crystal grain boundary, being the element with the deformability raising effect making steel, in order to effectively play such effect, preferably making Cr contain more than 0.2%.But if make Cr contain superfluously, then resistance to deformation increases, and cold-workability likely reduces, and therefore recommend its content to be less than 2%, be recommended in less than 1.5% further, special recommendation is below 1%.
In addition, Mo has the element that the hardness of the steel after making processing and deformability increase this effect, and in order to effectively play such effect, preferred Mo contains more than 0.04%, more preferably makes it containing more than 0.08%.But if make Mo contain superfluously, then cold-workability is likely deteriorated, therefore recommends its content to be less than 2%, be more recommended as less than 1.5%, special recommendation is less than 1%.
< from below Ti:0.2% (not containing 0%), at least one > selected in the group that below Nb:0.2% (not containing 0%), below V:0.2% (not containing 0%) are formed
The avidity of these elements and N is strong, coexists and forms N compound, make the crystal grain miniaturization of steel with N, and the toughness of the processed goods obtained after making cold working improves, and in addition, is have the element making resistance to anti-thread breakage this effect of raising.But, even if each element makes it to contain higher than higher limit, also all can not get characteristic improving effect.The content of each element is recommended as less than 0.2% respectively, is more recommended as 0.001 ~ 0.15%, and special recommendation is 0.002 ~ 0.1%.
Below < B:0.005% (not containing 0%) >
B is same with above-mentioned Ti, Nb and V, strong with the avidity of N, coexists and forms N compound, make the crystal grain miniaturization of steel with N, and the toughness of the processed goods obtained after making cold working improves, and in addition, is have the element making resistance to anti-thread breakage this effect of raising.Therefore, when steel plate of the present invention contains B, can guarantee that required solid solution N measures, the intensity after cold working is improved, therefore recommend its content to be less than 0.005%, be more recommended as 0.0001 ~ 0.0035%, special recommendation is 0.0002 ~ 0.002%.
At least one > that < selects from the group that below Cu:5% (not containing 0%), below Ni:5% (not containing 0%), below Co:5% (not containing 0%) are formed
These elements all have makes steel generation strain aging, makes it the effect of hardening, and is effective element for intensity after raising processing.In order to effectively play such effect, these elements preferably containing more than 0.1%, more preferably make it containing more than 0.3% respectively.But, if the content of these elements is superfluous, then make the effect of steel generation strain aging and sclerosis, after making processing in addition, strength-enhancing effect is saturated, in addition, also likely promotes crackle, therefore be recommended as less than 5% respectively, be more recommended as less than 4%, special recommendation is less than 3%.
< from below Ca:0.05% (not containing 0%), below REM:0.05% (not containing 0%), below Mg:0.02% (not containing 0%), below Li:0.02% (not containing 0%), below Pb:0.5% (not containing 0%), below Bi:0.5% (not containing 0%) form at least one > selected group
Ca makes the vulcanizing compounds system inclusion balling of MnS etc., is the deformability improving steel, and contributes to the element of machinability raising.In order to effectively play such effect, Ca preferably makes it containing more than 0.0005%, more preferably containing more than 0.001%.But even if contain superfluously, its effect is also saturated, can not expect the effect corresponding to content, therefore be recommended as less than 0.05%, more be recommended as less than 0.03%, and special recommendation is less than 0.01%.
REM and Ca is same, makes the vulcanizing compounds system inclusion balling of MnS etc., is the deformability improving steel, and contributes to the element of machinability raising.In order to effectively play such effect, REM preferably makes it, containing more than 0.0005%, more preferably to make it containing more than 0.001%.But even if contain superfluously, its effect is also saturated, can not expect the effect corresponding to content, therefore be recommended as less than 0.05%, more be recommended as less than 0.03%, and special recommendation is less than 0.01%.
Further, in the present invention, so-called REM, is meant to containing lanthanon (15 elements from La to Ln) and Sc (scandium) and Y (yttrium).Among these elements, the element preferably containing at least one selected from the group that La, Ce and Y are formed, more preferably containing La and/or Ce.
Mg and Ca is same, makes the vulcanizing compounds system inclusion balling of MnS etc., is the deformability improving steel, and contributes to the element of machinability raising.In order to effectively play such effect, Mg preferably makes it containing more than 0.0002%, more preferably containing more than 0.0005%.But even if contain superfluously, its effect is also saturated, can not expect the effect corresponding to content, therefore be recommended as less than 0.02%, more be recommended as less than 0.015%, and special recommendation is less than 0.01%.
Li and Ca is same, makes the vulcanizing compounds system inclusion balling of MnS etc., can improve the deformability of steel, in addition, Al system oxide compound eutectic is revealed and there is no evilization, is the element contributing to machinability raising.In order to effectively play such effect, Li preferably makes it containing more than 0.0002%, more preferably containing more than 0.0005%.But even if contain superfluously, its effect is also saturated, can not expect the effect corresponding to content, therefore be recommended as less than 0.02%, more be recommended as less than 0.015%, and special recommendation is less than 0.01%.
Pb is effective element for raising machinability.In order to effectively play such effect, Pb preferably makes it containing more than 0.005%, more preferably containing more than 0.01%.But contain if make it, then the problem that the generation of roll spot etc. manufactures occurs, and be therefore recommended as less than 0.5%, be more recommended as less than 0.4%, special recommendation is less than 0.3% superfluously.
Bi and Pb is same, is be effective element for improving in machinability.In order to effectively play such effect, Bi preferably makes it containing more than 0.005%, more preferably containing more than 0.01%.But even if make it to contain superfluously, the effect that machinability improves also is saturated, and be therefore recommended as less than 0.5%, be more recommended as less than 0.4%, special recommendation is less than 0.3%.
Next, imparting steel plate of the present invention is described with the set tissue of feature.
(the set tissue of steel plate of the present invention)
As above-mentioned, steel plate of the present invention, with ferrite body, or based on ferrite-pearlite multiphase steel, but its feature particularly by the plate planar orientation of ferrite crystal grain and size control thereof at specified range.
The set tissue of steel plate of the present invention, is formed with the heterogeneous structure of ferrite and pearlite.If perlite exists superfluously, then make the plasticity deterioration of steel plate, therefore perlite is preferably less than 10% in area occupation ratio, is more preferably less than 9%, is particularly preferably less than 8%.Surplus is ferrite.
< about be present in degree of depth t/4 (t: thickness of slab, lower with.) the ferrite crystal grain of position, plate planar orientation is relative to the area occupation ratio of the ferrite crystal grain of (123) face within 10 °: more than 20%, plate planar orientation is relative to the area occupation ratio of the ferrite crystal grain of (111) face within 10 °: more than 5%, and plate planar orientation is relative to the area occupation ratio of the ferrite crystal grain of (001) face within 10 °: less than 20% >
The generation type of set tissue, even if crystal system is identical, because working method difference also can difference to some extent, when rolled stock, is showed by rolling surface and rolling direction.In the present invention, show with rolling surface (〇 〇 〇).Further, 〇 represents integer.About the performance of its each orientation, describe and write in Long Island Shanxi one: among " set tissue " (Wan Shan Co., Ltd. periodical) etc.
In the present invention, about the ferrite crystal grain of position being present in degree of depth t/4, plate planar orientation, respectively the area occupation ratio relative to the ferrite crystal grain of (123) face within 10 ° is controlled more than 20%, control more than 5% relative to the area occupation ratio of the ferrite crystal grain of (111) face within 10 °, control below 20% relative to the area occupation ratio of the ferrite crystal grain of (001) face within 10 °, thus the drawing and forming of hot-rolled steel sheet can be improved.
All the time, about the plate planar orientation of ferrite crystal grain, the known raising for deep drawability effectively, makes (111) planar orientation being parallel to plate face very flourishing, on the other hand, weakens (001) planar orientation.In the operation implementing cold rolling process and annealing operation, the control of such plate planar orientation can be carried out, but in hot-rolled process, and, as the steel sheet of thickness of slab 2 ~ 15mm and so on, in the hot-rolled steel sheet of wall thickness, be then difficult to the control carrying out such plate planar orientation.
Therefore in the present invention, by again importing the ferrite crystal grain with the plate planar orientation in (123) face, the set organizational controls in hot-rolled sheet can be carried out, plasticity can be realized and improve.
As above-mentioned, there is as plate planar orientation the ferrite crystal grain in (123) face, there is the effect that plasticity, deep drawability are improved, in order to effectively play such effect, needing in area occupation ratio more than 20%.Be preferably more than 22%, be more preferably more than 24%, be particularly preferably more than 26%.
(111) face also has the effect that plasticity, deep drawing plasticity are improved, and in order to effectively play such effect, needs for more than 5% in area occupation ratio, is preferably more than 6%, is more preferably more than 8%.
(001) intra-face anisotropy that face makes shaping cause produces, and makes plasticity deterioration.Therefore, area occupation ratio is limited in less than 20%, preferably below 18%, more preferably below 15%.
Further, the tissue morphology of hot-rolled steel sheet, has tissue distribution in thickness of slab direction, but with 1/4 of thickness of slab depth location representatively position and specify tissue morphology.Think in addition, plate planar orientation has substantially equal effect relative to above-mentioned each desirable planar orientation ((123) face, (111) face, (001) face) ferrite crystal grain within 10 °, therefore specifies respectively with the area occupation ratio of the ferrite crystal grain with the plate planar orientation of this scope.
< is present in the median size of the ferrite crystal grain of the position of degree of depth t/4: 3 ~ 35 μm of >
Form the median size of the ferrite crystal grain of ferritic structure, the processibility (drawing processibility, bendability, press workability) of steel plate is improved, and meet the surface texture after processing, therefore need the scope at 3 ~ 35 μm.If ferrite crystal grain is meticulous, then resistance to deformation becomes too high, and therefore its median size is more than 3 μm, is preferably more than 4 μm, is more preferably more than 5 μm.On the other hand, if ferrite crystal grain is coarsening too, the then deterioration such as toughness, fatigue characteristic, further, even if crystallization control orientation, bendability and the extrusion molding to swell etc. still significantly reduce, crackle during shaping and coarse etc. bad easy generation, therefore its median size is less than 35 μm, is preferably less than 30 μm, is more preferably less than 28 μm.Further, as described above, in hot-rolled steel sheet, there is the distribution of sizes of ferrite crystal grain in thickness of slab direction, but representatively carry out the median size of regulation ferrite crystal grain in position with the depth location of 1/4 of thickness of slab.
(measuring method of the area occupation ratio of each phase)
About the area occupation ratio of above-mentioned each phase, nital corrosion can be carried out for each for examination steel plate, utilize scanning electron microscope (SEM; Multiplying power 1000 times) shooting 5 visuals field, each ratio of ferrite and pearlite is tried to achieve with a computing method.
(measuring method of the plate planar orientation of ferrite crystal grain)
The plate planar orientation of ferrite crystal grain, by SEM-EBSP, [Electron Back ScatteringPattern, and EBSD (Electron Back Scattering Diffraction), carry out Measurement and analysis.As SEM device, use such as NEC society SEM (JEOLJSM5410) respectively, EBSP measuring and analysis system, such as EBSP:TSL society system (OIM).In addition, although also according to the size of crystal grain, the measured zone of test portion is 300 ~ 1000 μm × 300 ~ 1000 μm, measures stepped intervals and is such as less than 1 ~ 3 μm.According to the crystalline orientation of each ferrite crystal grain so identified, amount to the area relative to the orientation of above-mentioned each desirable planar orientation within 10 °, try to achieve total area, divided by the area of measured zone, try to achieve the area occupation ratio of each desirable planar orientation.
(measuring method of the median size of ferrite crystal grain)
The median size of above-mentioned ferrite crystal grain, uses above-mentioned SEM-EBSP and measuring condition thereof, measures the maximum diameter of viewed each ferrite crystal grain in set measured zone respectively, is tried to achieve by its mean value as median size.
Then, below illustrate for the preferred manufacture method of yesterday to the invention described above steel plate.
(the preferred manufacture method of steel plate of the present invention)
The manufacture of steel plate of the present invention, if the raw steel with mentioned component composition can be configured as the method for the thickness of slab of expection, then following which kind of method carries out can.Such as, it carries out by condition shown below, can having the molten steel of mentioned component composition by modulation in converter, after becoming slab, is rolled into the hot-rolled steel sheet of expection thickness of slab by ingot casting or continuous casting.
[modulation of molten steel]
About the content of the N in molten steel, when carrying out melting in converter, the raw material of N compound can be contained by interpolation in molten steel, and/or by the control climate of converter at N
2adjust under atmosphere.
[heating]
Heating before hot rolling is carried out with 1100 ~ 1300 DEG C.Add at this and hanker, in order to not make N compound generate, and making many N solid solutions as far as possible, needing the heating condition of high temperature.The preferred lower limit of Heating temperature is 1100 DEG C, and preferred lower limit is 1150 DEG C.On the other hand, operationally have any problem higher than the temperature of 1300 DEG C.
[hot rolling]
Hot rolling is carried out in the mode making finishing temperature and reach more than 870 DEG C.If excessively make finishing temperature low temperature, then because ferrite transformation can at high temperature occur, the carbide precipitate coarsening in ferrite, fatigue strength deterioration, so need certain above finishing temperature.In order to make austenite crystal coarsening increase ferritic particle diameter to a certain extent, finishing temperature is more preferably more than 900 DEG C.Further, because temperature guarantees difficulty, so the upper limit of finishing temperature is 1000 DEG C.
[hot rolling table]
The thickness of slab of hot-rolled steel sheet of the present invention is 2 ~ 15mm, but in order to make ferrite crystal grain miniaturization, its median size is controlled in set particle size range, so not only need to control above-mentioned rolling temperature, and needs the final draft making the tandem rolling of finish to gauge to be more than 15%.Usually, finish to gauge is the tandem rolling of enforcement 5 ~ 7 passage, but based on plate nip control viewpoint and set pass sequence, final draft terminates in about 12 ~ 13%.Above-mentioned final draft is preferably more than 16%, is more preferably more than 17%.Above-mentioned final draft is higher, is 20%, 30%, then can obtain making the effect of crystal grain more miniaturization, but based on the viewpoint of roll control, the upper limit is defined as about 30%.
[roll speed of hot rolling]
As above-mentioned, in order to obtain the set tissue of the ferrite crystal grain with plate planar orientation, even as much as possible in order to make the set organizational controls in thickness of slab direction obtain in addition, also need the roll speed controlling finish to gauge.Therefore, the roll speed of final passage is controlled at 300 ~ 700m/min.No matter be that roll speed is too high, or too low, can to obtain the plate planar orientation of expecting, the set in thickness of slab direction is organized and is easily become uneven and be not preferred in addition.When China and foreign countries' roll speed is slow, productivity is also deteriorated.Be preferably 350 ~ 650m/min, be more preferably 400 ~ 600m/min.
[chilling after hot rolling]
After above-mentioned finish to gauge terminates, with the speed of cooling of 20 DEG C/more than s (the first chilling speed) chilling within 5s, with more than 580 DEG C, stop chilling lower than the temperature of 670 DEG C (chilling stopping temperature).This is the tissue in order to obtain ferrite body, and namely perlite divides the ferrite-pearlite heterogeneous structure of rate in allowed band.When speed of cooling (chilling speed) is lower than 20 DEG C/s, pearlitic transformation is promoted, or, when chilling stops temperature lower than 580 DEG C, pearlitic transformation or bainitic transformation are promoted, all be difficult to obtain the ferrite pearlific steel of perlite point rate in allowed band, the set tissue into expection can not be controlled, the deterioration of drawing processibility, bendability.On the other hand, if chilling stops temperature to be more than 670 DEG C, then the carbide precipitate coarsening in ferrite, equally, the deterioration of drawing processibility, bendability.Chilling stops temperature being preferably 600 ~ 650 DEG C, is more preferably 610 ~ 640 DEG C.
[slow cooling after chilling stopping]
After above-mentioned chilling stops, by letting cool or air cooling, with the speed of cooling of 10 DEG C/below s (slow cooling speed) slow cooling 5 ~ 20s.Carry out ferritic formation fully on one side thus, make the carbide precipitate moderately miniaturization in ferrite.Speed of cooling higher than 10 DEG C/s, or the slow cooling time lower than 5s time, ferritic formation volume is not enough, and can not control the set tissue into expection, and drawing processibility, bendability are deteriorated.On the other hand, if the slow cooling time is higher than 20s, carbide precipitate can not coarsening, fatigue strength deterioration.
[chilling after slow cooling, batches]
After above-mentioned slow cooling, once again with the speed of cooling of 20 DEG C/more than s (the second chilling speed) chilling, batching higher than 300 DEG C, less than 450 DEG C.This is the tissue in order to become ferrite body, also expects, by carrying out set organization formation, to guarantee drawing processibility, bendability.Speed of cooling (the second chilling speed) lower than 20 DEG C/s, or coiling temperature higher than 450 DEG C time, perlite is formed in a large number, on the other hand when lower than 300 DEG C, forms martensite and retained austenite, the deterioration of drawing processibility, bendability.
Below, illustrate in greater detail the present invention by embodiment, but following embodiment does not limit character of the present invention, also can before can meeting aim described later scope in suitably changed enforcement, these are all included in the scope of technology of the present invention.
[embodiment]
By vacuum melting method, the steel that the one-tenth shown in the following table 1 of melting is grouped into, is cast as the ingot bar of thickness 120mm, implements hot rolling with the condition shown in following table 2 to it, makes hot-rolled steel sheet.Further, no matter in which test, the speed of cooling stopped by the end of chilling after finish to gauge terminates is 20 DEG C/more than s, and the cooling after chilling stops is with the condition of the speed of cooling slow cooling 5 ~ 20s of 10 DEG C/below s.
For the hot-rolled steel sheet so obtained, by according to each measuring method illustrated by above-mentioned [mode for carrying out an invention], try to achieve the area occupation ratio of each phase and the plate planar orientation of ferrite crystal grain and median size organized in solid solution N amount, steel plate.
In addition, about the drawing processibility of above-mentioned hot-rolled steel sheet, be the steel plate of thickness of slab about 4 ~ 10mm, but evaluate with cylinder forming test.Drift is of a size of φ 100mm, and drift shoulder is R8mm, and die diameter is φ 103mm, and punch die shoulder is R8mm.In " the drawing ratio " of billet diameter (D) for the ratio (D/d) of the diameter (d) of cylinder, if rupture through 1 drawing, when the maximum billet diameter that can shrink cylinder is Dmax, Dmax/d is defined as " limited drawing ratio " (LDR (Limiting Drawing Ratio)), using it as evaluation index.Then, LDR be 2 ~ 2.1 for qualified.
In addition, the test film after being shaped is taken out, the outside of visual observation cylindrical portion and flange portion.The result of visual observation, during the generation of visible crack be ×, not there is crackle, but as seen can be visual crack time be △, small as seen concavo-convex (gauffer), but be 〇 when there is not crack is ◎ when the generation of gauffer also has no.Then, ◎ or 〇 is qualified.Further, " crackle " is with the difference in " crack ", and the maximum width in gap is that more than 1mm is defined as " crackle ", is defined as in " crack " lower than 1mm.
In addition, measure the hardness of the surface element of the flange part after above-mentioned drawing processing experiment, evaluate the surface hardness after processing.Use Vickers pyramid hardness testing machine, with load: 1000g, measuring position: the D/4 position central part (D: diameter of part) in test film cross section and pendulous frequency: the condition of 5 times, measures the Vickers' hardness (Hv) of test film after each processing.Then, more than 250Hv's is qualified.
These measuring results are presented in following table 3.Also have, with " ferrite crystal grain " statement of " (〇 〇 〇) face (%) " on hurdle in table, be meant to the area occupation ratio (unit: %) of plate planar orientation relative to (〇 〇 〇) face ferrite crystal grain within 10 °.
[table 1]
(one: without adding, underscore: scope of the present invention is outer)
[table 2]
(outside underscore=scope of the present invention, *=recommended range is outer)
[table 3]
(outside underscore=scope of the present invention, outside *=recommended range,
Surface texture: ◎ is very good, and 〇 is good, and there is crack on △ surface, and × cracking occurs,
One: unmeasured because there is crackle
Invention steel: [LDR=2.0 ~ 2.1] and [surface texture=◎ or 〇] and [processing rear surface hardness >=≡≤250Hv],
Comparative steel: the situation not meeting the condition of foregoing invention steel)
As shown in table 3, steel No.1,2,7 ~ 14,25 ~ 31 all employs and meets the steel grade that one-tenth of the present invention is grouped into the important document of regulation, with the hot-rolled condition manufacture recommended, consequently make the invention steel of the important document abundance of organization prescribed of the present invention, drawing processibility and processing rear surface hardness all meet criterion of acceptability, can confirm that can obtain both work in-processes demonstrates good drawing processibility, demonstrates again the hot-rolled steel sheet of set surface hardness (intensity) after processing.
In contrast, steel No.3 ~ 6,15 ~ 24 do not meet comparative steel at least some among important document that one-tenth given to this invention is grouped into and organizes, among drawing processibility and processing rear surface hardness, at least any one does not meet criterion of acceptability.
Such as, although steel No.3 meets into the important document be grouped into, but the finishing temperature when Heating temperature before hot rolling, hot rolling and the chilling after hot rolling stop temperature departing from recommended range and too low, solid solution N quantity not sufficient, and (123) ferrite crystal grain of planar orientation is not enough, the ferrite crystal grain of (001) planar orientation is superfluous on the other hand, drawing processibility, processing rear surface hardness also inequality.
In addition, although steel No.4 meets into the important document be grouped into, but thickness of slab after hot rolling departs from specialized range and excessive, (123) ferrite crystal grain of planar orientation, (111) planar orientation is all not enough, the ferrite crystal grain of (001) planar orientation becomes superfluous on the other hand, and ferrite crystal grain coarsening, at least drawing poor in processability.
In addition, although steel No.5 meets into the important document be grouped into, but the roll speed of final passage during hot rolling departs from recommended range and excessive, (123) ferrite crystal grain of planar orientation is not enough, on the other hand, (001) ferrite crystal grain of planar orientation is superfluous, drawing poor in processability.
In addition, although steel No.6 meets into the important document be grouped into, final draft during hot rolling departs from recommended range and too small, ferrite crystal grain coarsening, at least drawing poor in processability.
In addition, steel No.15 (steel grade j), although hot-rolled condition is in recommended range, N content is too low, therefore solid solution N quantity not sufficient, processing rear surface difference of hardness.
On the other hand, steel No.16 (steel grade k), although hot-rolled condition is in recommended range, N content is too high, at least drawing poor in processability.
In addition, steel No.17 (steel grade l), although hot-rolled condition is in recommended range, then C content is too high, solid solution N quantity not sufficient, processing rear surface difference of hardness.
In addition, steel No.18 (steel grade m) although hot-rolled condition is in recommended range, Si too high levels, the ferrite crystal grain of (123) planar orientation is not enough, the ferrite crystal grain of (001) planar orientation is superfluous on the other hand, at least drawing poor in processability.
In addition, steel No.19 (steel grade n) is although hot-rolled condition is in recommended range, and Mn content is too low, and the ferrite crystal grain of (001) planar orientation becomes superfluous, drawing processibility, processing rear surface hardness inequality.
On the other hand, steel No.20 (steel grade o) although hot-rolled condition is in recommended range, Mn too high levels, the ferrite crystal grain of (123) planar orientation is not enough, the ferrite crystal grain of (001) planar orientation becomes superfluous on the other hand, at least drawing poor in processability.
In addition, steel No.21 (steel grade p) although hot-rolled condition is in recommended range, P too high levels, the ferrite crystal grain of (123) planar orientation is not enough, the ferrite crystal grain of (001) planar orientation becomes superfluous on the other hand, at least drawing poor in processability.
In addition, steel No.22 (steel grade q) is although hot-rolled condition is in recommended range, but S too high levels, (123) planar orientation, (111) ferrite crystal grain of planar orientation is not enough, the ferrite crystal grain of (001) planar orientation becomes superfluous on the other hand, at least drawing poor in processability.
In addition, steel No.23 (steel grade r) is although hot-rolled condition is in recommended range, and Al content is too low, and the ferrite crystal grain of (123) planar orientation is not enough, the ferrite crystal grain of (001) planar orientation becomes superfluous on the other hand, at least drawing poor in processability.
On the other hand, steel No.24 (steel grade s) although hot-rolled condition is in recommended range, Al too high levels, the ferrite crystal grain of (123) planar orientation is not enough, the ferrite crystal grain of (001) planar orientation becomes superfluous on the other hand, at least drawing poor in processability.
By confirming suitability of the present invention above.
In detail and describe the present invention with reference to specific embodiment, but do not depart from the spirit and scope of the present invention and can in addition various changes and modifications, this is concerning very clear practitioner.
The application is based on the Japanese patent application (patent application 2013-053564) applied on March 15th, 2013, and its content is quoted in this reference.
[utilizability in industry]
Hot-rolled steel sheet of the present invention, for the transmission mechanism part and housing etc. of the gear etc. of automobile, can realize its lightweight high-intensity.
Claims (2)
1. a hot-rolled steel sheet for drawing processibility and the surface hardness excellence after processing, it is characterized in that, thickness of slab is 2 ~ 15mm,
Become to be grouped in mass % for (following, relate to chemical composition all with)
Below C:0.3% (not containing 0%),
Below Si:0.5% (not containing 0%),
Mn：0.2～1％、
Below P:0.05% (not containing 0%),
Below S:0.05% (not containing 0%),
Al：0.01～0.1％、
N：0.008～0.025％、
Surplus is made up of iron and inevitable impurity,
More than solid solution N:0.007%,
About being present in the ferrite crystal grain that the degree of depth is the position of t/4 (t: thickness of slab, lower same),
Plate planar orientation is more than 20% relative to the area occupation ratio of the ferrite crystal grain of (123) face within 10 °,
Plate planar orientation is more than 5% relative to the area occupation ratio of the ferrite crystal grain of (111) face within 10 °,
Plate planar orientation is less than 20% relative to the area occupation ratio of the ferrite crystal grain of (001) face within 10 °,
Further, to be present in the described degree of depth be the median size of the ferrite crystal grain of the position of t/4 is 3 ~ 35 μm.
2. hot-rolled steel sheet according to claim 1, wherein, becomes to be grouped into also containing at least one in (a) ~ (e),
At least one in (a) below Cr:2% (not containing 0%) and below Mo:2% (not containing 0%);
At least one in (b) below Ti:0.2% (not containing 0%), below Nb:0.2% (not containing 0%) and below V:0.2% (not containing 0%);
(c) below B:0.005% (not containing 0%);
At least one in (d) below Cu:5% (not containing 0%), below Ni:5% (not containing 0%) and below Co:5% (not containing 0%);
At least one in (e) below Ca:0.05% (not containing 0%), below REM:0.05% (not containing 0%), below Mg:0.02% (not containing 0%), below Li:0.02% (not containing 0%), below Pb:0.5% (not containing 0%) and below Bi:0.5% (not containing 0%).
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2013053564A JP6177551B2 (en) | 2013-03-15 | 2013-03-15 | Hot-rolled steel sheet with excellent drawability and surface hardness after processing |
| JP2013-053564 | 2013-03-15 | ||
| PCT/JP2014/055296 WO2014141919A1 (en) | 2013-03-15 | 2014-03-03 | Hot-rolled steel sheet having excellent drawability and post-processing surface hardness |
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| Publication Number | Publication Date |
|---|---|
| CN105026596A true CN105026596A (en) | 2015-11-04 |
| CN105026596B CN105026596B (en) | 2016-12-14 |
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| CN201480011947.0A Expired - Fee Related CN105026596B (en) | 2013-03-15 | 2014-03-03 | The hot rolled steel plate of the case hardness excellence after drawing processability and processing |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US20160002745A1 (en) |
| JP (1) | JP6177551B2 (en) |
| CN (1) | CN105026596B (en) |
| TW (1) | TWI527909B (en) |
| WO (1) | WO2014141919A1 (en) |
Cited By (3)
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| CN114318170A (en) * | 2021-12-19 | 2022-04-12 | 江阴市江扬标准紧固件制造有限公司 | High-strength corrosion-resistant flange bolt for automobile and preparation process thereof |
| CN114729426A (en) * | 2019-11-20 | 2022-07-08 | 杰富意钢铁株式会社 | Hot-rolled steel sheet for electric resistance welded steel pipe and method for producing same, line pipe, and building structure |
| CN116024502A (en) * | 2022-12-29 | 2023-04-28 | 中国重汽集团济南动力有限公司 | High-strength high-elongation light saddle shell and preparation method thereof |
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| JP6143355B2 (en) * | 2013-10-22 | 2017-06-07 | 株式会社神戸製鋼所 | Hot-rolled steel sheet with excellent drawability and surface hardness after carburizing heat treatment |
| WO2017022025A1 (en) * | 2015-07-31 | 2017-02-09 | 新日鐵住金株式会社 | High-strength hot-rolled steel sheet |
| MX2018006851A (en) | 2015-12-11 | 2018-08-01 | Nippon Steel & Sumitomo Metal Corp | Molded product manufacturing method and molded product. |
| CN106148803B (en) * | 2016-08-30 | 2017-11-24 | 唐山钢铁集团有限责任公司 | A kind of production method of deep-draw battery case steel |
| KR102321319B1 (en) * | 2019-12-19 | 2021-11-03 | 주식회사 포스코 | Steel sheet having excellent ductility and low-temperature impact toughness and method for manufacturing thereof |
| WO2023140239A1 (en) * | 2022-01-21 | 2023-07-27 | 日本製鉄株式会社 | Cold-rolled steel sheet and manufacturing method thereof |
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| JP2003321715A (en) * | 2002-04-26 | 2003-11-14 | Jfe Steel Kk | Method of producing galvanized hot rolled steel sheet having excellent stain aging hardening property |
| JP2004323925A (en) * | 2003-04-25 | 2004-11-18 | Nippon Steel Corp | Strain aging hardening type steel sheet having excellent cold elongation deterioration resistance, cold delayed aging property and low temperature bake hardenability, and its production method |
| JP2007291514A (en) * | 2006-03-28 | 2007-11-08 | Jfe Steel Kk | Hot-rolled steel sheet with small in-plane anisotropy after cold rolling and recrystallization annealing, cold-rolled steel sheet with small in-plane anisotropy and production method therefor |
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| CN114729426A (en) * | 2019-11-20 | 2022-07-08 | 杰富意钢铁株式会社 | Hot-rolled steel sheet for electric resistance welded steel pipe and method for producing same, line pipe, and building structure |
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| CN116024502A (en) * | 2022-12-29 | 2023-04-28 | 中国重汽集团济南动力有限公司 | High-strength high-elongation light saddle shell and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN105026596B (en) | 2016-12-14 |
| TWI527909B (en) | 2016-04-01 |
| US20160002745A1 (en) | 2016-01-07 |
| WO2014141919A1 (en) | 2014-09-18 |
| TW201506171A (en) | 2015-02-16 |
| JP6177551B2 (en) | 2017-08-09 |
| JP2014177686A (en) | 2014-09-25 |
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