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CN105026596B - The hot rolled steel plate of the case hardness excellence after drawing processability and processing - Google Patents

The hot rolled steel plate of the case hardness excellence after drawing processability and processing Download PDF

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Publication number
CN105026596B
CN105026596B CN201480011947.0A CN201480011947A CN105026596B CN 105026596 B CN105026596 B CN 105026596B CN 201480011947 A CN201480011947 A CN 201480011947A CN 105026596 B CN105026596 B CN 105026596B
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crystal grain
steel
steel plate
ferrite crystal
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CN105026596A (en
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梶原桂
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Kobe Steel Ltd
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Kobe Steel Ltd
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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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

nullA kind of hot rolled steel plate，Its thickness of slab is 2～15mm，One-tenth is grouped into，In terms of quality %，Below C:0.3%、Below Si:0.5%、Mn:0.2～1%、Below P:0.05%、Below S:0.05%、Al:0.01～0.1%、N:0.008～0.025%，Surplus is made up of ferrum and inevitable impurity，More than solid solution N:0.007%，Ferrite crystal grain about the position being present in degree of depth t/4 (t: thickness of slab)，Plate planar orientation is more than 20% relative to the area occupation ratio of (123) face crystal grain within 10 °，It is more than 5% relative to the area occupation ratio of (111) face crystal grain within 10 °，It is less than 20% relative to the area occupation ratio of (001) face crystal grain within 10 °，And the mean diameter being present in the ferrite crystal grain of the position of described degree of depth t/4 is 3～35 μm.

Description

The hot rolled steel plate of the case hardness excellence after drawing processability and processing
Technical field
The present invention relates to both work in-processes and demonstrate good drawing processability, demonstrate set surface the most after processing The hot rolled steel plate of hardness.
Background technology
In recent years, from the viewpoint of environmental conservation, rise to purpose with the fuel efficiency of automobile, various the zero of automobile Part, the such as lightweight to the steel for the actuating device part of gear etc. and housing etc., i.e. with the requirement of high intensity more Send out surging.In order to comply with the requirement of such lightweight high-intensity, as the steel generally used, it is possible to use bar steel The steel (forge hot material) of forge hot are carried out.It addition, in order to cut down the CO in part manufacturing process2Discharge capacity, up to now, close Cold forging in the part of the gear etc. processed through forge hot requires the most surging.
So, cold working (cold forging), compare with hot-working and temperature processing, have productivity ratio high, and dimensional accuracy and steel The best sharp point of yield rate.But, when manufacturing part by such cold working, structure is debatable, in order to by cold rnning The intensity of the part of work guarantees more than the predetermined value expected, is necessarily required to the steel using intensity, i.e. deformation drag high Material., the deformation drag of the steel used is the highest, more can cause the lost of life of cold working metal die, Er Qieyou The difficult point of crackle it is susceptible to during cold working.
Therefore, the method always implemented is, is being become by steel cold forging both after shaped, is carrying out at the heat of Q-tempering etc. Reason, thus manufacture and guarantee the high intensity part in set intensity (hardness).But, the heat treatment after cold forging, accessory size must So can change, the machining being therefore accomplished by Secondary ground cutting etc. is revised, and this just expects that one can save Slightly heat treatment and subsequent the solution countermeasure of processing.
In order to solve above-mentioned problem, such as, disclose in mild steel, utilize solid solution C, the carrying out of suppression room temperature ageing, borrow Guarantee set age-hardening amount by strain-aging, thus obtain the cold forging wire rod bar steel (ginseng of excellent in distortion aging property According to patent documentation 1).
But, this technology only measures controlled strain timeliness by solid solution C, and obtains the institute after sufficient cold-workability and processing The steel that the hardness strength needed is existed side by side are had any problem.
Therefore, the applicant, it is conceived to the solid solution C contained by steel and solid solution N and deformation drag and static strain timeliness are made The difference of the impact become, has carried out various research, and it is it was found that by the amount suitably controlling these solid solution elements, then can Access both work in-processes and play good cold-workability, after cold working (cold forging), demonstrate set case hardness again The mechanical realization steel of (intensity), and have been carried out patent application (with reference to patent documentation 2).
These steel achieve the existing side by side of high rigidity (high intensity) after cold-workability and processing, but with above-mentioned patent literary composition Offering the wire rod bar steel described in 1 same, it is forge hot material, has the difficult point that manufacturing cost is high.Therefore, in order to make manufacturing cost lower Cost, replaces existing forge hot material, is also studied with the technology that hot rolled steel plate makes automobile part by cold working.
Such as, propose there is one after nitrogen treatment, it is possible to obtain high surface hardness and the nitridation of sufficient hardening depth The hot rolled steel plate (with reference to patent documentation 3) processed.
But, this technology needs to carry out nitrogen treatment after cold working again, has and can not realize asking of sufficient cost degradation Topic.
Additionally, it is also proposed that have a kind of hot rolled steel plate, consisting of, containing below C:0.10%, Si: less than 0.01%, Mn: Less than 1.5% and below Al:0.20%, and contain in the range of (Ti+Nb)/2:0.05～0.50%, with S:0.005% Below, below N:0.005%, below O:0.004%, the mode being aggregated in less than 0.0100% of S, N and O contain above unit Element, and the ferrite homogeneous structure of the essence making microscopic structure be more than 95%, this hot rolled steel plate, precision punching machined surface Dimensional accuracy is excellent, and the case hardness of the punch side after processing is high, and the most resistance to red rust defective is also excellent (with reference to patent Document 4).
But, this hot rolled steel plate, N is that harmful element is limited in extremely low content, with the application that N is positively utilized The hot rolled steel plate of invention, the most entirely different in technology.
In general, about in order to improve the set organizational controls that the formability of steel plate is carried out than ever mutually, it is used for The steel-sheet deep drawing processability of the body panel of automobile, plastic anisotropy's (r value (Lankford value): stretching of material Plate width strain in test and the ratio of thickness of slab strain) the biggest, its processability is the highest, in this external recrystallization set tissue, makes to put down Row in plate planar orientation 111} face is the most flourishing, weaken 100} planar orientation, integral for the raising of deep drawability, This point is confirmed (with reference to non-patent literature 1) the most.
Therefore, carry out all set organizational controls by steel plate and improve the effort of processability.
Such as, proposing there is a kind of high-strength steel sheet, it is in terms of quality %, 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 range of this external satisfaction Ti-(48/12) C-(48/14) N-(48/32) S >=-0.03%, remaining Amount is made up of Fe and inevitable impurity, wherein, with the deviation of the hardness of this steel plate divided by the value of its meansigma methods be 0.2 with Under, and, rolling direction { the face intensity in 110} face is less than 1.7, punching hole expandability excellent (with reference to patent documentation 5).
It addition, propose there is a kind of high-strength steel sheet, it is in terms of quality %, containing C: higher than 0.0005% and be less than 0.10%, below Si:1.5%, more than Mn:0.1% and 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 from below Nb:0.20% and Ti: Among less than 0.20% select one or both, surplus was made up of Fe and forming of inevitable impurity, about structure of steel, Counting more than 60% as ferritic phase with volume fraction, with the density function (ODF) of three-dimensional crystals orientation, { φ 1, Φ, φ 2} counts, Φ Being 0 °, φ 1 is 0 °, and φ 2 is ODF{0 ° when 45 °, 0 °, 45 ° } intensity below 3.0, and Φ is 35 °, and φ 1 is 0 °, φ 2 is ODF{0 ° when 45 °, 35 °, 45 ° } the scope that intensity is more than 2.5, less than 4.5, using the teaching of the invention it is possible to provide difficult when extrusion molding With cracking, and the high-strength steel sheet (with reference to patent documentation 6) that the anisotropy of ductility is little.
Proposing there is a kind of hot rolled steel plate, it has following composition, i.e. in terms of quality %, containing C:0.01～0.05%, Si: Less than 0.2%, below Mn:0.50%, Al:0.005～0.10%, below P:0.05%, below S:0.05%, N:0.01% with Under, below O:0.01%, surplus is made up of Fe and inevitable impurity, and its to have such as undertissue, i.e. average crystal grain straight Footpath is that the ferritic phase of 40～60 μm is single-phase, and, 118} ＜ 110 ＞ and the random strength of 115} ＜ 110 ＞ than respectively 10 with On, { 111} ＜ 110 ＞ is with { the random strength ratio respectively 1 of 111} ＜ 121 ＞ is with undertissue, using the teaching of the invention it is possible to provide cold rolling-recrystallization annealing After the little hot rolled steel plate of intra-face anisotropy (with reference to patent documentation 7).
Such as above example, the formability raising being attempted steel plate by set organizational controls has carried out all, and major part relates to And be the outside plate of automobile, body framing material, chassis part.In the present invention as the actuating device part of the gear etc. of object With in housing etc., required formability is different from Automobile body parts, is not require nothing more than drawing processability and pultrusion processability Deng, require the part of the case hardness after processing the most as described so.
It addition, in the field of actuating device part, from the forged article of bar steel () such as forge hot, cold forging, light with part Quantify, the research of part manufacture that cost degradation is target and is carried out by steel plate is also carrying out, and is requiring further formability.
[look-ahead technique document]
[patent documentation]
[patent documentation 1] Japanese Laid-Open flat 10-306345 publication
[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: " recrystallization set tissue and the application towards this organizational controls are tied again The forefront of brilliant research ", in March, 1999, p.208
Summary of the invention
Currently invention addresses above-mentioned situation and formed, its object is to, it is provided that a kind of both work in-processes demonstrate good Drawing processability, demonstrates the hot rolled steel plate of set case hardness the most after processing.
First invention, is the hot rolled steel plate that the case hardness after drawing processability and processing is excellent, it is characterised in that
Thickness of slab is 2～15mm,
One-tenth is grouped into,
With quality % be calculated as (following, relate to chemical composition all with.),
Below C:0.3% (without 0%),
Below Si:0.5% (without 0%),
Mn:0.2～1%,
Below P:0.05% (without 0%),
Below S:0.05% (without 0%),
Al:0.01～0.1%,
N:0.008～0.025%,
Surplus by ferrum 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 plate planar orientation (123) face ferrite crystal grain within 10 ° relatively is more than 20%,
The area occupation ratio of plate planar orientation (111) face ferrite crystal grain within 10 ° relatively is more than 5%,
The area occupation ratio of plate planar orientation (001) face ferrite crystal grain within 10 ° relatively is less than 20%,
Further, the mean diameter of the ferrite crystal grain being present in the position of described degree of depth t/4 is 3～35 μm.
Second invention, is according to the steel plate described in the first invention, wherein,
Become to be grouped into possibly together with below Cr:2% (without 0%) and/or below Mo:2% (without 0%).
3rd invention, is according to the first or two hot rolled steel plate described in invention, wherein,
Become be grouped into possibly together with from
Below Ti:0.2% (without 0%),
Below Nb:0.2% (without 0%),
At least one selected in the group that below V:0.2% (without 0%) is constituted.
4th invention, is according to the first～three hot rolled steel plate according to any one of invention, wherein,
Become to be grouped into possibly together with below B:0.005% (without 0%).
5th invention, is according to the first～four hot rolled steel plate according to any one of invention, wherein,
Become be grouped into possibly together with from
Below Cu:5% (without 0%),
Below Ni:5% (without 0%),
At least one selected in the group that below Co:5% (without 0%) is constituted.
6th invention, is according to the first～five hot rolled steel plate according to any one of invention, wherein,
Become be grouped into possibly together with from
Below Ca:0.05% (without 0%),
Below REM:0.05% (without 0%),
Below Mg:0.02% (without 0%),
Below Li:0.02% (without 0%),
Below Pb:0.5% (without 0%),
At least one selected in the group that below Bi:0.5% (without 0%) is constituted.
According to the present invention, in there is the tissue of ferrite body of set mean diameter, by assuring that solid solution N amount, And it is set tissue morphology by the set organizational controls of hot rolled steel plate, even if in the part requiring drawing processability, logical Cross the deformability improved in processing, still can extend the life-span of metal die still, and steel plate can be provided to be difficult to crackle, Part obtained by after processing is able to ensure that the hot rolled steel plate of set case hardness.
Detailed description of the invention
Hereinafter, for the hot rolled steel plate of the present invention (hereinafter also referred to as " steel plate of the present invention " or be only called " steel plate ".), more It is illustrated in detail.Steel plate of the present invention, with the forge hot material described in above-mentioned patent documentation 2, is total to by this point of guaranteeing N solid solution capacity Logical, but allowing C content to improve cutoff range, control the set tissue morphology of steel plate, and make ferrite crystal grain miniaturization Aspect is 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 as object.When thickness of slab is less than 2mm, it is impossible to guarantee conduct The rigidity of structure.On the other hand, if thickness of slab is higher than 15mm, then it is difficult to reach the set tissue morphology of regulation in the present invention, Effect is improved less than intended drawing processability.Preferably thickness of slab is 3～14mm.
Secondly, the one-tenth for composition steel plate of the present invention is grouped into and illustrates.Hereinafter, the unit of chemical composition is entirely matter Amount %.
(one-tenth of steel plate of the present invention is grouped into)
Below ＜ C:0.3% (without 0%) ＞
C is the element that the formation of the tissue to steel plate causes tremendous influence, although tissue is ferrite body tissue, or ferrum Ferritic-pearlite heterogeneous structure, but the ferrite body tissue the fewest in order to become pearlite, it is to need to limit The element of content.If make C contain superfluously, then the pearlite in steel plate tissue divides rate to rise, owing to the processing of pearlite is hardened, It is likely to result in deformation drag 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 below 0.15%.But, if the content of C is very few, then the deoxidation in the melting of steel becomes Obtain difficult, and be difficult to the intensity after meeting deep drawing processing, case hardness, the most preferably more than 0.0005%, more preferably It is more than 0.0008%, particularly preferably more than 0.001%.
Below ＜ Si:0.5% (without 0%) ＞
Si makes the deformation drag of steel plate increase by solid solution in steel, is therefore the element needing to do one's utmost to reduce.To this end, Si content in steel plate, is limited in less than 0.5% to suppress the increase of deformation drag, preferably below 0.45%, more excellent It is selected in less than 0.4%, particularly preferably below 0.3%.But, if the content of Si is few, then the difficulty of the deoxidation in melting, and Be difficult to meet the intensity after deep drawing processing, case hardness, the most preferably more than 0.005%, more preferably 0.008% with On, particularly preferably more than 0.01%.
＜ Mn:0.2～1% ＞
Mn is the element of effect at steelmaking process with deoxidation and desulfurization.When improving the content of N in steel in addition, by The dynamic strain aging that heating in processing causes, causes crackle to be susceptible to, but then, and processing when at this moment Mn makes Property improve, have suppression crackle effect.In order to effectively play these effects, the Mn content in steel is more than 0.2%, excellent Elect more than 0.22% as, more preferably more than 0.25%.But, if Mn content is superfluous, then deformation drag is excessive, occurs because of segregation The inhomogeneities of the tissue caused, is therefore less than 1%, preferably less than 0.98%, more preferably less than 0.95%.
Below ＜ P:0.05% (without 0%) ＞
P is the impurity element inevitably contained in steel, if but its contained in ferrite, then at ferrite Grain boundary segregation and make cold-workability deteriorate, it addition, it makes higher content strengthen, be to constitute the unit of reason that deformation drag increases Element.Therefore, the content of P, from the viewpoint of cold-workability, is preferably done one's utmost to reduce, but extreme minimizing can be caused steel-making cost Increase, be therefore less than 0.05% in view of process capability, preferably less than 0.03%.
Below ＜ S:0.05% (without 0%) ＞
S also with P again it is inevitable impurity, as FeS at crystal grain boundary with membranaceous precipitation, be to make processability bad The element changed.Hot short effect is caused it addition, also have.Therefore, from the viewpoint of improving deformability, the present invention makes S Content is less than 0.05%, preferably less than 0.03%.But, make S content reach 0 and industrially have any problem.Further, S has Make the effect that machinability improves, therefore from the viewpoint of machinability improves, it is recommended that be preferably allowed to containing more than 0.002%, more Preferably comprise more than 0.006%.
＜ Al:0.01～0.1% ＞
Al is to be element effective to deoxidation in steelmaking process.Al content in order to obtain the effect of this deoxidation, in steel It is more than 0.01%, preferably more than 0.015%, more preferably more than 0.02%.But, if the content of Al is superfluous, then make tough Property reduce, crackle is susceptible to, and is therefore less than 0.1%, preferably less than 0.09%, more preferably less than 0.08%.
＜ N:0.008～0.025% ＞
N by processing after static strain timeliness under, be the important element for obtaining set intensity.Therefore, steel N content in material is more than 0.008%, preferably more than 0.0085%, more preferably more than 0.009%.But, if N's contains Amount surplus, then, in addition to static strain timeliness, the impact of the dynamic strain aging in processing is also notable, and deformation drag increase is not Suitably, therefore it is less than 0.025%, preferably less than 0.023%, 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 amount ".) solid solution N, it is possible to less make change Form drag improves, and promotes static strain timeliness.In order to ensure intensity required after cold working, solid solution N amount needs to be 0.007% Above.But, if solid solution N amount surplus, then cold-workability deterioration, the most preferably less than 0.03%.Further, N in steel Content is less than 0.025%, and the most substantially solid solution N amount does not reaches more than 0.025%.
Here, the solid solution N amount of the present invention, it is based on JIS G 1228, the total N content from steel deducts N compound total The amount measured and try to achieve.The measurement method of the practicality of this solid solution N illustrated below amount.
(a) Inert Gas Fusion Method-thermal conductivity method (measurement of total N content)
By putting into crucible from the sample for cutting on examination material, melt in inert gas flow and extract N, abstract is removed Deliver to conductance cell and measure the change of thermal conductance, try to achieve total N content.
(b) ammonia separated indophenol blue absorption photometry (measurement of N total amount of compound)
By from the sample for cutting on examination material, dissolve in 10%AA system electrolyte, carry out constant-current electrolysis, measure in steel N total amount of compound.The 10%AA system electrolyte used, is made up of 10% acetone, 10% tetramethyl-ammonium chloride, surplus methanol The electrolyte of non-aqueous solvent, is the solution that will not make steel Surface Creation passive state epithelium.
Make the sample about 0.5g for examination material, dissolve in this 10%AA system electrolyte, with the Merlon of hole dimension 0.1 μm The filter of system, filters the insoluble residue (N compound) generated.The insoluble residue that will obtain, at sulphuric acid, potassium sulfate and fine copper Heat resolve in chip processed, makes analyte be combined with filtrate.After making this solution alkaline with sodium hydroxide, carry out steam Distillation, absorbs the ammonia distillated with dilute sulfuric acid.Add again phenol ferment, sodium hypochlorite and pentacyano nitroso-group ferrum (III) acid sodium (ペ Application タ シ ア ノ ニ ト ロ シ Le ferrum (III) acid Na ト リ ウ system) and generate blue complex, use absorption spectrophotometry to measure extinction Degree, tries to achieve N total amount of compound.
Then, from the total N content tried to achieve by the method for above-mentioned (a), deduct the N compound tried to achieve by the method for above-mentioned (b) Total amount, then can try to achieve solid solution N amount.
The base steel of the present invention is originally containing mentioned component, and surplus is ferrum and inevitable impurity, but in addition, is not damaging In the range of the effect of the evil present invention, additionally it is possible to add following permission composition.
Below ＜ Cr:2% (without 0%) and/or below Mo:2% (without 0%) ＞
Cr improves the intensity of crystal grain boundary, is the element of the deformability raising effect having and making steel, in order to effectively send out Wave such effect, preferably make Cr contain more than 0.2%.But, if make Cr contain superfluously, then deformation drag increases, cold rnning Work is likely to decrease, and therefore recommending its content is less than 2%, it is further recommended that below 1.5%, special recommendation 1% with Under.
It addition, Mo is to have the hardness of the steel after making processing and deformability increases the element of this effect, in order to have Effect ground plays such effect, preferably Mo and contains more than 0.04%, is more preferably allowed to containing more than 0.08%.But, if making Mo Contain, then cold-workability likely deteriorates superfluously, and therefore recommending its content is less than 2%, is more recommended as less than 1.5%, spy It is not recommended as less than 1%.
＜ is from below Ti:0.2% (without 0%), below Nb:0.2% (without 0%), below V:0.2% (without 0%) At least one ＞ selected in the group constituted
These elements are strong with the affinity of N, coexist with N and form N compound, make the crystal grain miniaturization of steel, make cold working After the toughness of processed goods that obtains improve, it addition, be the element having and making resistance to anti-thread breakage this effect of raising.But, each element Even if above higher limit be allowed to containing, the most all can not get characteristic improving effect.The content of each element be recommended as respectively 0.2% with Under, more it being recommended as 0.001～0.15%, special recommendation is 0.002～0.1%.
Below ＜ B:0.005% (without 0%) ＞
B is as above-mentioned Ti, Nb and V, strong with the affinity of N, coexists with N and forms N compound, and the crystal grain making steel is fine Changing, the toughness of the processed goods obtained after making cold working improves, it addition, be the element having and making resistance to anti-thread breakage this effect of raising. Therefore, when the steel plate of the present invention contains B, it can be ensured that required solid solution N amount, make the intensity after cold working improve, therefore recommend Its content is less than 0.005%, is more recommended as 0.0001～0.0035%, and special recommendation is 0.0002～0.002%.
＜ is constituted from below Cu:5% (without 0%), below Ni:5% (without 0%), below Co:5% (without 0%) Group in select at least one ＞
These elements are respectively provided with and make steel generation strain-aging, are allowed to the effect of hardening, for intensity after improving processing are Effective element.In order to effectively play such effect, these elements preferably comprise more than 0.1% respectively, are more preferably allowed to Containing more than 0.3%.But, if the content of these elements is superfluous, then make steel generation strain-aging and the effect of hardening, also have After making processing, strength-enhancing effect is saturated, it addition, it is also possible to promote crackle, be recommended as less than 5% the most respectively, be more recommended as Less than 4%, special recommendation is less than 3%.
＜ (does not contains from below Ca:0.05% (without 0%), below REM:0.05% (without 0%), below Mg:0.02% 0%), below Li:0.02% (without 0%), below Pb:0.5% (without 0%), below Bi:0.5% (without 0%) are constituted At least one ＞ selected in Qun
Ca makes the vulcanizing compounds system field trash spheroidizing of MnS etc., is the deformability improving steel, and contributes to cutting Property improve element.In order to effectively play such effect, Ca is preferably allowed to, containing more than 0.0005%, more preferably contain More than 0.001%.But, even if contain superfluously, its effect is also saturated, it is impossible to expect effect corresponding with content, therefore Being recommended as less than 0.05%, be more recommended as less than 0.03%, special recommendation is less than 0.01%.
As REM with Ca, make the vulcanizing compounds system field trash spheroidizing of MnS etc., be the deformability improving steel, and Contribute to the element that machinability improves.In order to effectively play such effect, REM is preferably allowed to containing more than 0.0005%, More preferably it is allowed to containing more than 0.001%.But, even if contain superfluously, its effect is also saturated, it is impossible to expect and content phase The effect answered, is therefore recommended as less than 0.05%, is more recommended as less than 0.03%, and special recommendation is less than 0.01%.
Further, in the present invention, so-called REM, the meaning is containing lanthanide series (from the 15 of La to Ln elements) and Sc (scandium) and Y (yttrium).Among these elements, preferably comprise the unit of at least one selected from the group that La, Ce and Y are constituted Element, more preferably contains La and/or Ce.
As Mg with Ca, make the vulcanizing compounds system field trash spheroidizing of MnS etc., be the deformability improving steel, and Contribute to the element that machinability improves.In order to effectively play such effect, Mg is preferably allowed to containing more than 0.0002%, more Preferably comprise more than 0.0005%.But, even if contain superfluously, its effect is also saturated, it is impossible to expect corresponding with content Effect, is therefore recommended as less than 0.02%, is more recommended as less than 0.015%, and special recommendation is less than 0.01%.
As Li with Ca, make the vulcanizing compounds system field trash spheroidizing of MnS etc., it is possible to increase the deformability of steel, separately Outward, make Al system oxide eutectic reveal and there is no evilization, contribute to the element that machinability improves.Such in order to effectively play Effect, Li is preferably allowed to, containing more than 0.0002%, more preferably contain more than 0.0005%.But, even if contain superfluously, its Effect is also saturated, it is impossible to expects effect corresponding with content, is therefore recommended as less than 0.02%, be more recommended as 0.015% with Under, special recommendation is less than 0.01%.
Pb is effective element for improving machinability.In order to effectively play such effect, Pb be preferably allowed to containing More than 0.005%, more preferably contain more than 0.01%.But, if be allowed to contain superfluously, then occur the generation etc. of roll speckle to make The problem made, is therefore recommended as less than 0.5%, is more recommended as less than 0.4%, and special recommendation is less than 0.3%.
Bi Yu Pb is again it is being used for improving in machinability is effective element.In order to effectively play such effect, Bi Preferably it is allowed to, containing more than 0.005%, more preferably contain more than 0.01%.But, even if be allowed to contain superfluously, machinability carries High effect is also saturated, is therefore recommended as less than 0.5%, is more recommended as less than 0.4%, and special recommendation is less than 0.3%.
It follows that illustrate with the set tissue of feature for giving steel plate of the present invention.
(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 particular range.
The set tissue of steel plate of the present invention, is constituted with the heterogeneous structure of ferrite and pearlite.If pearlite is deposited superfluously , then make the formability of steel plate deteriorate, therefore pearlite is preferably less than 10%, more preferably less than 9% in terms of area occupation ratio, spy You Xuanwei 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 relative to (123) area occupation ratio of face ferrite crystal grain within 10 °: more than 20%, plate planar orientation relative to (111) face within 10 ° The area occupation ratio of ferrite crystal grain: more than 5%, plate planar orientation is relative to the area of (001) face ferrite crystal grain within 10 ° Rate: less than 20% ＞
The generation type of set tissue, even if system of crystallization is identical, owing to processing method difference also can difference, rolled stock In the case of, rolling surface and rolling direction show.In the present invention, show with rolling surface ().Further, represent whole Number.The performance being respectively orientated about it, is described in Long Island Shanxi one and writes: among " set tissue " (Wan Shan Co., Ltd. periodical) etc..
In the present invention, about the ferrite crystal grain of the position being present in degree of depth t/4, plate planar orientation, respectively will be relative to (123) area occupation ratio of face ferrite crystal grain within 10 ° controls more than 20%, relative to (111) face ferrum within 10 ° The area occupation ratio of ferritic crystal grain controls more than 5%, controls relative to the area occupation ratio of (001) face ferrite crystal grain within 10 ° Below 20% such that it is able to improve the drawing and forming of hot rolled steel plate.
All the time, about the plate planar orientation of ferrite crystal grain, it is known that for deep drawability raising effectively, make to put down Row (111) planar orientation in plate face is the most flourishing, on the other hand, weakens (001) planar orientation.Implementing cold rolling process and lehr attendant In the operation of sequence, the control of such plate planar orientation can be carried out, but in hot-rolled process, and, as thickness of slab 2～15mm Etc sheet metal, the hot rolled steel plate of wall thickness is then difficult to the control of such plate planar orientation.
The most in the present invention, by again importing the ferrite crystal grain of the plate planar orientation with (123) face, can carry out Set organizational controls in hot rolled plate, it is possible to realize formability and improve.
As above-mentioned, there is as plate planar orientation the ferrite crystal grain in (123) face, have and make formability, deep drawability improve Effect, in order to effectively play such effect, need in terms of area occupation ratio more than 20%.Preferably more than 22%, more excellent Elect more than 24% as, particularly preferably more than 26%.
(111) face also has the effect making formability, deep drawing formability improve, in order to effectively play such work With, need to be more than 5% in terms of area occupation ratio, preferably more than 6%, more preferably more than 8%.
(001) intra-face anisotropy that face makes shaping cause produces, and makes formability deteriorate.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 plate, there is tissue distribution in thickness of slab direction, but the degree of depth position of 1/4 with thickness of slab Put as representing position and regulation tissue morphology.It is additionally contemplated that, plate planar orientation relative to above-mentioned each preferable planar orientation ((123) face, (111) face, (001) face) ferrite crystal grain within 10 ° has the most equal effect, therefore to have the plate of this scope The area occupation ratio of the ferrite crystal grain of planar orientation specifies respectively.
＜ is present in the mean diameter of the ferrite crystal grain of the position of degree of depth t/4: 3～35 μm ＞
Constituting the mean diameter of ferrite crystal grain of ferritic structure, (drawing processability, bending add to make the processability of steel plate Work, press workability) improve, and meet the surface texture after processing, it is therefore desirable in the scope of 3～35 μm.If ferrum is plain Body crystal grain is meticulous, then deformation drag becomes too high, and therefore its mean diameter is more than 3 μm, more than preferably 4 μm, more preferably It is more than 5 μm.On the other hand, if ferrite crystal grain excessively coarsening, the then deterioration such as toughness, fatigue properties, and, even if controlling Crystalline orientation, bendability and the extrusion molding swollen etc. still significantly reduce, crackle during shaping and coarse etc. bad Being susceptible to, therefore its mean diameter is below 35 μm, below preferably 30 μm, below more preferably 28 μm.Further, with above-mentioned Equally, in hot rolled steel plate, there is the distribution of sizes of ferrite crystal grain in thickness of slab direction, but the depth location of 1/4 with thickness of slab As the mean diameter representing position and coming regulation ferrite crystal grain.
(measuring method of the area occupation ratio of each phase)
Area occupation ratio about above-mentioned each phase, it is possible to carrying out nital corrosion for each for examination steel plate, utilization is swept Retouch type ultramicroscope (SEM；Multiplying power 1000 times) 5 visuals field of shooting, with a calculating method try to achieve ferrite and pearlite respectively than Rate.
(measuring method of the plate planar orientation of ferrite crystal grain)
The plate planar orientation of ferrite crystal grain, by SEM-EBSP [Electron Back Scattering Pattern, With EBSD (Electron Back Scattering Diffraction), measure analysis.As SEM device, respectively Use such as NEC society SEM (JEOLJSM5410), EBSP measuring and analysis system, such as EBSP:TSL society system (OIM). Although it addition, also according to the size of crystal grain, but the measured zone of test portion is 300～1000 μ m 300～1000 μm, measures stepping Below for example, 1～3 μm of interval.According to the crystalline orientation of each ferrite crystal grain so identified, amount to relative to above-mentioned respectively The area of preferable planar orientation orientation within 10 °, tries to achieve total area, divided by the area of measured zone, tries to achieve each preferable face The area occupation ratio of orientation.
(measuring method of the mean diameter of ferrite crystal grain)
The mean diameter of above-mentioned ferrite crystal grain, uses above-mentioned SEM-EBSP and measuring condition thereof, measures set respectively In measured zone, the maximum gauge of viewed each ferrite crystal grain, is averaged value and tries to achieve as mean diameter.
Then, following description is 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 intended thickness of slab can be configured to by the raw steel with mentioned component composition Method, then following which kind of method carries out can.Such as, it is carried out can be by condition shown below, by converter Modulation has the molten steel of mentioned component composition, after becoming slab by ingot casting or continuous casting, is rolled into expection thickness of slab Hot rolled steel plate.
[modulation of molten steel]
About the content of the N in molten steel, when carrying out melting in converter, it is possible to by adding containing N chemical combination in molten steel The raw material of thing, and/or by the control climate of converter at N2It is adjusted 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 to the greatest extent may be used Many N solid solutions can be made, need the heating condition of high temperature.The preferred lower limit of heating-up temperature is 1100 DEG C, and preferred lower limit is 1150℃.On the other hand, the temperature higher than 1300 DEG C is operationally had any problem.
[hot rolling]
Hot rolling is carried out in the way of making finishing temperature reach more than 870 DEG C.If excessively making finishing temperature low temperature, then because Ferrite transformation can at high temperature occur, the carbide precipitate coarsening in ferrite, and fatigue strength deteriorates, so needing certain Above finishing temperature.Increasing ferritic particle diameter to a certain extent to make austenite crystal coarsening, finishing temperature is more It is 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 the hot rolled steel plate of the present invention is 2～15mm, but in order to make ferrite crystal grain miniaturization, is averaged grain Footpath controls in set particle size range, so not only needing to control above-mentioned rolling temperature, and need to make the tandem rolling of finish to gauge Final reduction ratio is more than 15%.Generally, finish to gauge be implement 5～7 passages tandem rolling, but based on plate nip control viewpoint and Setting pass schedule, final reduction ratio terminates in 12～about 13%.Above-mentioned final reduction ratio is preferably more than 16%, more preferably More than 17%.Above-mentioned final reduction ratio is the highest, 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%.
[mill speed of hot rolling]
As above-mentioned, in order to obtain the set tissue with the ferrite crystal grain of plate planar orientation, in addition to make thickness of slab direction Set organizational controls obtain the most uniform, it is also desirable to control finish to gauge mill speed.Therefore, by the rolling speed of final passage Degree controls 300～700m/min.Either mill speed is too high, or too low, can be to obtain intended plate planar orientation, separately The set tissue in outer thickness of slab direction easily becomes uneven and is not preferred.When mill speed is slow at home and abroad, productivity ratio is also deteriorated.Excellent Elect 350～650m/min as, more preferably 400～600m/min.
[chilling after hot rolling]
After above-mentioned finish to gauge terminates, with rate of cooling (the first chilling speed) chilling of 20 DEG C/more than s within 5s, with 580 Temperature (chilling stopping temperature) more than DEG C, less than 670 DEG C stops chilling.This is the tissue in order to obtain ferrite body, i.e. Pearlite divides rate ferrite-pearlite heterogeneous structure in allowed band.Rate of cooling (chilling speed) is less than 20 DEG C/s Time, pearlitic transformation is promoted, or, when chilling stops temperature less than 580 DEG C, pearlitic transformation or bainitic transformation are promoted Enter, be all difficult to the ferrite pearlific steel obtaining pearlite point rate in allowed band, it is impossible to control as intended collection charge-coupled Knitting, drawing processability, bendability deteriorate.On the other hand, if it is more than 670 DEG C that chilling stops temperature, then in ferrite Carbide precipitate coarsening, equally, drawing processability, bendability deteriorate.Chilling stops temperature and is preferably 600～650 DEG C, More preferably 610～640 DEG C.
[slow cooling after chilling stopping]
After above-mentioned chilling stops, by letting cool or air cooling, with rate of cooling (slow cooling speed) slow cooling 5 of 10 DEG C/below s～ 20s.Thus while being sufficiently carried out ferritic formation, make the moderately miniaturization of the carbide precipitate in ferrite.Cold But speed is higher than 10 DEG C/s, or when the slow cooling time is less than 5s, ferritic formation amount is not enough, and not can be controlled to intended collection Charge-coupled knitting, drawing processability, bendability deteriorate.On the other hand, if the slow cooling time is higher than 20s, carbide precipitate will not be thick Bigization, fatigue strength deteriorates.
[chilling after slow cooling, batch]
After above-mentioned slow cooling, once again with rate of cooling (the second chilling speed) chilling of 20 DEG C/more than s, higher than 300 DEG C, Less than 450 DEG C are batched.This is the tissue in order to become ferrite body, it is also desirable to organize the formation of by carrying out set, it is ensured that draw Deep processing, bendability.Rate of cooling (the second chilling speed) is less than 20 DEG C/s, or when coiling temperature is higher than 450 DEG C, pearl Body of light is formed in a large number, on the other hand when less than 300 DEG C, forms martensite and retained austenite, drawing processability, bending machining Property deterioration.
Hereinafter, illustrate in greater detail the present invention by embodiment, but following embodiment does not limit the character of the present invention, Can suitably be changed enforcement before can meeting in the range of objective described later, these are all contained in the skill of the present invention The scope of art.
[embodiment]
By vacuum melting method, the steel that the one-tenth shown in melting table 1 below is grouped into, it is cast as the ingot bar of thickness 120mm, with Applying heat in fact is rolled by the condition shown in table 2 below, makes hot rolled steel plate.Further, no matter in which is tested, finish to gauge cuts after terminating The rate of cooling only stopped to chilling is 20 DEG C/more than s, and the cooling after chilling stops is with the rate of cooling of 10 DEG C/below s The condition of slow cooling 5～20s.
For so obtained hot rolled steel plate, by according to the respectively side of measurement illustrated by above-mentioned [by the way of carrying out an invention] Method, tries to achieve the area occupation ratio of each phase and the plate planar orientation of ferrite crystal grain and mean diameter organized in solid solution N amount, steel plate.
It addition, about the drawing processability of above-mentioned hot rolled steel plate, be the steel plate of thickness of slab 4～about 10mm, but become with cylinder Shape test evaluation.Drift a size of φ 100mm, drift shoulder is R8mm, and die diameter is φ 103mm, and punch die shoulder is R8mm.With steel Base diameter (D) is for " drawing ratio " meter of the ratio (D/d) of the diameter (d) of cylinder, if rupturing through 1 drawing, it is possible to When the billet diameter of the maximum shrinking 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.
It addition, take out the test film after shaping, visualization cylindrical portion and the outside of flange portion.The knot of visualization Really, it is seen that during the generation of crackle be ×, there is not crackle, but visible can be visual crack time be △, it is seen that small is recessed Convex (gauffer), but be to be ◎ when the generation of gauffer also has no when there is not crack.Then, ◎ or qualified.Further, " crackle " is with the difference in " crack ", the Breadth Maximum in gap be the definition of more than 1mm be " crackle ", less than the definition of 1mm For " crack ".
It addition, measure the hardness of the surface element of the flange part after above-mentioned drawing processing experiment, evaluate the surface after processing hard Degree.Use Vickers pyramid hardness testing machine, with load: 1000g, measurement position: D/4 position central part (D: the part in test film cross section Diameter) and pendulous frequency: the condition of 5 times, measure the Vickers hardness (Hv) of test film after each processing.Then, more than 250Hv's is Qualified.
These measurement results show in Table 3 below.Further, with " () on " ferrite crystal grain " hurdle in table Face (%) " statement, it is (single relative to the area occupation ratio of () face ferrite crystal grain within 10 ° that the meaning is plate planar orientation Position: %).
[table 1]
(one: without adding, underscore: the scope of the present invention is outer)
[table 2]
(outside underscore=the scope of the present invention, *=recommended range is outer)
[table 3]
(outside underscore=the scope of the present invention, outside *=recommended range,
Surface texture: ◎ is very good, and well, 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] and [processing rear surface hardness >=≡≤ 250Hv],
Relatively steel: be unsatisfactory for the situation of the condition of foregoing invention steel)
As shown in table 3, steel No.1,2,7～14,25～31 all employ and meet the one-tenth of the present invention and be grouped into the important document of regulation Steel grade, with the hot-rolled condition manufacture recommended, its result is the invention steel that the important document of the organization prescribed making the present invention is sufficient, drawing Processability and processing rear surface hardness all meet criterion of acceptability, it is possible to confirm that available both work in-processes demonstrate good drawing Deep processing, demonstrates the hot rolled steel plate of set case hardness (intensity) the most after processing.
In contrast, steel No.3～6,15～24 be unsatisfactory for important document that one-tenth given to this invention is grouped into and organizes it In at least at least any one is unsatisfactory for qualified mark among some comparison steel, drawing processability and processing rear surface hardness Accurate.
Such as, although steel No.3 meets into the important document being grouped into, but the finish to gauge temperature when heating-up temperature before hot rolling, hot rolling Chilling after degree and hot rolling stops temperature and departs from recommended range and too low, and solid solution N measure deficiency, and the ferrum of (123) planar orientation is plain Body crystal grain is not enough, and on the other hand the ferrite crystal grain of (001) planar orientation is superfluous, and drawing processability, processing rear surface hardness are the most equal Difference.
Although it addition, steel No.4 meets into the important document being grouped into, but the thickness of slab after hot rolling departs from prescribed limit and excessive, (123) planar orientation, (111) planar orientation ferrite crystal grain the most not enough, on the other hand the ferrite crystal grain of (001) planar orientation becomes Surplus, and ferrite crystal grain coarsening, at least drawing poor in processability.
Although it addition, steel No.5 meets into the important document being grouped into, but the mill speed of final passage during hot rolling departs from Recommended range and excessive, the ferrite crystal grain of (123) planar orientation is not enough, on the other hand, the ferrite crystal grain mistake of (001) planar orientation Surplus, drawing poor in processability.
It addition, although steel No.6 meets into the important document being grouped into, final reduction ratio during hot rolling departs from recommended range and mistake Little, ferrite crystal grain coarsening, at least drawing poor in processability.
It addition, steel No.15 (steel grade j), although hot-rolled condition is in recommended range, but N content is too low, therefore solid solution N amount Deficiency, processing rear surface difference of hardness.
On the other hand, steel No.16 (steel grade k), although hot-rolled condition is in recommended range, but N content is too high, at least drawing Poor in processability.
It addition, steel No.17 (steel grade l), although hot-rolled condition is in recommended range, then C content is too high, and solid solution N measures deficiency, Processing rear surface difference of hardness.
It addition, steel No.18 (although steel grade m) hot-rolled condition is in recommended range, but Si too high levels, (123) planar orientation Ferrite crystal grain not enough, on the other hand the ferrite crystal grain of (001) planar orientation is superfluous, at least drawing poor in processability.
It addition, steel No.19 (although steel grade n) hot-rolled condition is in recommended range, but Mn content is too low, and (001) face takes To ferrite crystal grain become superfluous, drawing processability, processing rear surface hardness inequality.
On the other hand, steel No.20 (although steel grade o) hot-rolled condition is in recommended range, but Mn too high levels, (123) face The ferrite crystal grain of orientation is not enough, and on the other hand the ferrite crystal grain of (001) planar orientation becomes superfluous, at least drawing processability Difference.
It addition, steel No.21 (although steel grade p) hot-rolled condition is in recommended range, but P content is too high, (123) planar orientation Ferrite crystal grain not enough, on the other hand the ferrite crystal grain of (001) planar orientation becomes superfluous, at least drawing poor in processability.
It addition, steel No.22 (although steel grade q) hot-rolled condition is in recommended range, but S too high levels, (123) face takes To, the ferrite crystal grain of (111) planar orientation is not enough, and on the other hand the ferrite crystal grain of (001) planar orientation becomes superfluous, at least draws Deep processing is poor.
It addition, steel No.23 (although steel grade r) hot-rolled condition is in recommended range, but Al content is too low, and (123) face takes To ferrite crystal grain not enough, on the other hand the ferrite crystal grain of (001) planar orientation becomes superfluous, at least drawing poor in processability.
On the other hand, steel No.24 (although steel grade s) hot-rolled condition is in recommended range, but Al too high levels, (123) The ferrite crystal grain of planar orientation is not enough, and on the other hand the ferrite crystal grain of (001) planar orientation becomes superfluous, at least drawing processability Difference.
By the suitability being able to confirm that the present invention above.
In detail and illustrate the present invention with reference to specific embodiment, but can without departing from the spirit and scope of the present invention Various changes and modifications in addition, this will be apparent from for practitioner.
The application is based on Japanese patent application filed in 15 days March in 2013 (patent application 2013-053564), in it Hold and quote in this reference.
[industrial applicability]
The hot rolled steel plate of the present invention, for the actuating device part of gear etc. of automobile and housing etc., it is possible to realize it light Quantify high intensity.

Claims (2)

1. the hot rolled steel plate that case hardness after a drawing processability and processing is excellent, it is characterised in that thickness of slab be 2～ 15mm,
Become to be grouped into and be calculated as with quality %
Below C:0.3% but without 0%,
Below Si:0.5% but without 0%,
Mn:0.2～1%,
Below P:0.05% but without 0%,
Below S:0.05% but without 0%,
Al:0.01～0.1%,
N:0.008～0.025%,
Surplus is made up of ferrum and inevitable impurity,
More than solid solution N:0.007%,
About being present in the ferrite crystal grain of the position that the degree of depth is t/4, wherein, t is thickness of slab
Plate planar orientation is more than 20% relative to the area occupation ratio of (123) face ferrite crystal grain within 10 °,
Plate planar orientation is more than 5% relative to the area occupation ratio of (111) face ferrite crystal grain within 10 °,
Plate planar orientation is less than 20% relative to the area occupation ratio of (001) face ferrite crystal grain within 10 °,
Further, the mean diameter of the ferrite crystal grain being present in the position that the described degree of depth is t/4 is 3～35 μm.
Hot rolled steel plate the most according to claim 1, wherein, become be grouped in terms of quality % possibly together with in (a)～(e) extremely Few one,
(a) below Cr:2% but without 0% and below Mo:2% but without at least one in 0%；
(b) below Ti:0.2% but without 0%, below Nb:0.2% but without 0% and below V:0.2% but without in 0% At least one；
(c) below B:0.005% but without 0%；
(d) below Cu:5% but without 0%, below Ni:5% but without 0% and below Co:5% but without at least in 0% Kind；
(e) below Ca:0.05% but without 0%, below REM:0.05% but without 0%, below Mg:0.02% but without 0%, Below Li:0.02% but without 0%, below Pb:0.5% but without 0% and below Bi:0.5% but without at least in 0% Kind.
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WO2017022025A1 (en) * 2015-07-31 2017-02-09 新日鐵住金株式会社 High-strength hot-rolled steel sheet
WO2017098983A1 (en) 2015-12-11 2017-06-15 新日鐵住金株式会社 Molded product manufacturing method and molded product
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JP6973681B2 (en) * 2019-11-20 2021-12-01 Ｊｆｅスチール株式会社 Hot-rolled steel sheet for electric-sewn steel pipe and its manufacturing method, electric-sewn steel pipe and its manufacturing method, line pipe, building structure
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
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