CN109415791A - Property and hole expandability uniform in material excellent precipitation strength type hot rolled steel plate and its manufacturing method - Google Patents
Property and hole expandability uniform in material excellent precipitation strength type hot rolled steel plate and its manufacturing method Download PDFInfo
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- CN109415791A CN109415791A CN201780037469.4A CN201780037469A CN109415791A CN 109415791 A CN109415791 A CN 109415791A CN 201780037469 A CN201780037469 A CN 201780037469A CN 109415791 A CN109415791 A CN 109415791A
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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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/02—Hardening by precipitation
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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
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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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
- C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
- C21D8/0215—Rapid solidification; Thin strip casting
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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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- 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
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C—CHEMISTRY; METALLURGY
- 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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- 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
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
- C21D2211/004—Dispersions; Precipitations
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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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Abstract
An aspect of of the present present invention is related to a kind of property uniform in material and the excellent precipitation strength type hot rolled steel plate of hole expandability, and the hot rolled steel plate is in terms of weight %, comprising: C:0.02-0.05%；Si:0.01~0.3%；Mn:1.0~1.6%；Ti:0.04~0.1%；Nb:0.01~0.05%；N:0.008% or less the and Fe of surplus and other inevitable impurity, and meet following formula (1), the microstructure of the hot rolled steel plate includes the ferrite and (Ti of 95 area % or more, Nb) C miscible precipitate, being formed by diameter is 10nm (Ti below, Nb) C miscible precipitate quantity is the (Ti that diameter is more than 10nm, Nb) five times or more of C miscible precipitate quantity, formula (1): 0.35≤(Ti+Nb+V+Mo)/(C+N)≤0.70；Wherein, in the formula (1), each element symbol indicates the atomicity percentage composition (at.%) of each element, does not include that element in steel is calculated as 0.
Description
Technical field
The present invention relates to precipitation strength type hot rolled steel plates and its manufacturing method that a kind of property uniform in material and hole expandability are excellent.
Background technique
It is well known that in order to improve hole expandability, man-hour requirement is added to inhibit the generation of microcrack, and this microcrack
Generation is the concentration that deformed due to the grain boundaries when difference of hardness between hard phase and soft phase is larger in two-phase, so as to cause
Microcrack.
In this regard, disclosing in patent document 1 a kind of prevent microcrack by forming more bainite and ensures to expand
The transformation enhanced type steel grade of permeability.
Further, in order to maximize hole expandability ensure high intensity while, carried out by being utilized in ferrite main phase
The precipitating reinforcing effect of Ti, Nb, Mo, V, C etc. carry out the research and development that can ensure high-intensitive precipitation strength structural section.
A kind of technology is disclosed in patent document 2, is based on ferritic soft main phase matrix group by implementing in the technology
It knits, prevents the generation of microcrack caused by the difference of hardness between soft/hard phase in advance, thus the Ar after finish rolling3Nose and analysis
Under the conditions of Nose is consistent out, it is changed into the ferritic crystal grain of induction in the process from austenite and generates fine precipitation phenomenon,
To ensure intensity.
Compared to transformation enhanced type steel, the precipitation strength structural section of patent document 2 can ensure the intensity material of same levels
Matter, while further increasing and rushing edge processability.However, patent document 2 be related to it is a kind of slab is cooled to room temperature after carry out again plus
Heat and the manufacturing method based on traditional general rolling mill technology rolled, and have the following problems: due to according to heating
The inhomogeneities of pick-up behavior caused by width direction after fire bars part and rolling and the temperature deviation on length direction, so that steel
Material hardness, elongation percentage and in terms of there are material deviations.
On the other hand, it is well known that the new steel technique to attract attention in recent years is that is, so-called to utilize high-speed continuous casting and nothing
Head rolling (endless rolling) mode manufacture steel plate continuous endless rolling (Continuous Endless Mill,
CEM) technique in operational characteristic since the width direction of strip (strip) and the temperature deviation of length direction are small, can
Obtain the good steel of material deviation.
But such as patent document 3 and 4, most research and development all concentrates on the transformation of such as DP steel and TRIP steel
Enhanced type hot rolled steel plate.However, combination of the transformation enhanced type hot rolled steel plate due to soft/hard phase inevitable in organizing,
Therefore, it is difficult to ensure excellent to rush edge processability.
In addition, for solution strengthening type hot rolled steel plate, the high strength steel for being 590MPa or more in manufacture tensile strength
When, need largely to add the solution strengthening elements such as Si, Mn and Cr, therefore manufacturing cost is high.
On the contrary, precipitation strength structural section have the advantages that manufacturing cost is low and can ensure it is excellent rush edge processability, but
It is when manufacturing precipitation strength structural section by the CEM technique in the way of high-speed continuous casting and endless rolling, to have the following problems:
Generate casting crack, be precipitated as Ti, Nb and N etc. edge crack caused by element and relatively low final rolling temperature generation and
Logical plate reduction of steel plate caused by the resistance of deformation Behavioral change of the material by caused by the influence of Nb etc. etc..
Therefore, to solve the above-mentioned problems, needing to research and develop one kind can be applied to CEM technique, and property uniform in material and expansion
The excellent precipitation strength type hot rolled steel plate of permeability and its manufacturing method.
(existing technical literature)
Patent document 1: Japanese Laid-Open Patent Publication the 1994-200351st
Patent document 2: Japanese Laid-Open Patent Publication the 2003-321739th
Patent document 3: Korean Patent Laid the 2012-0049993rd
Patent document 4: Korean Patent Laid the 2012-0052022nd
Summary of the invention
(1) technical problems to be solved
According to an aspect of the present invention, its purpose is to provide the excellent precipitation of a kind of property uniform in material and hole expandability is strong
Change type hot rolled steel plate and its manufacturing method.
In addition, the technical problems to be solved by the invention are not limited to above content.Technology to be solved by this invention
Problem can understand that those skilled in the art can be readily appreciated that according to the entire content of this specification
Supplementary technology problem to be solved by this invention.
(2) technical solution
According to an aspect of the present invention, a kind of property uniform in material and the excellent precipitation strength type hot-rolled steel of hole expandability are provided
Plate, in terms of weight %, comprising: C:0.02-0.05%；Si:0.01~0.3%；Mn:1.0~1.6%；Ti:0.04~
0.1%；Nb:0.01~0.05%；N:0.008% or less the and Fe of surplus and other inevitable impurity, and meet with
Following formula (1), the microstructure of the hot rolled steel plate include the ferrite and (Ti, Nb) C miscible precipitate of 95 area % or more,
It is the compound analysis of (Ti, Nb) C that diameter is more than 10nm that be formed by diameter, which be 10nm (Ti, Nb) C miscible precipitate quantity below,
Five times or more of object quantity out, formula (1): 0.35≤(Ti+Nb+V+Mo)/(C+N)≤0.70；Wherein, in the formula (1), respectively
The symbol of element indicates the atomicity percentage composition (at.%) of each element, does not include that element in steel is calculated as 0.
In addition, according to another aspect of the present invention, a kind of property uniform in material and the excellent precipitation strength type of hole expandability are provided
The manufacturing method of hot rolled steel plate, comprising: continuous casting step carries out continuous casting to the molten steel for meeting above-mentioned composition of alloy, to manufacture thin plate
Base；Roughing step carries out roughing to the sheet billet, to obtain bar steel (bar)；Heating stepses heat the bar steel
Or concurrent heating；Finishing step carries out finish to gauge to the bar steel of heating, to obtain hot rolled steel plate；Cooling step, on the run-out table
The hot rolled steel plate is cooled to 600~700 DEG C with the cooling velocity of 30 DEG C/s or more, is then carried out air-cooled；And winding step
Suddenly, 450~600 DEG C at a temperature of the cooling hot rolled steel plate is wound.
In addition, the technical solution does not list all features of the invention.It can be found in following specific embodiments more
Add and various features and its advantage and effect of the invention are understood in detail.
(3) beneficial effect
In accordance with the invention it is possible to which providing a kind of tensile strength is 590MPa or more, and the material on width/height direction
Deviation compared to the excellent precipitation strength type hot rolled steel plate of uniform in material property and hole expandability of the average value within ± 5% range and its
Manufacturing method.
Detailed description of the invention
Fig. 1 is the photo of the microstructure of the example 1 shot by scanning electron microscope.
Fig. 2 is the photo of the microstructure of the comparative example 1 shot by scanning electron microscope.
Fig. 3 is the photo of the microstructure of the comparative example 7 shot by scanning electron microscope.
Preferred forms
In the following, being illustrated to the preferred embodiment of the present invention.However, embodiments of the present invention can be deformed into other
Various ways, the scope of the present invention are not limited to embodiments described below.Also, embodiments of the present invention be in order to
It is more absolutely proved to those of ordinary skill in the art of the invention and offer.
Present inventors have recognized that manufacturing precipitation strength type by the CEM technique in the way of high-speed continuous casting and continuous rolling
When steel, there is generation casting crack, the edge as caused by the precipitation element such as Ti, Nb and N and relatively low final rolling temperature is split
Steel caused by the resistance of deformation Behavioral change of the generation of line and the material by caused by the influence of Nb etc. leads to plate reduction etc.
Problem, to solve the above-mentioned problems, present inventor has performed in-depth studies.
As a result, it is thus identified that composition of alloy and manufacturing method can be controlled by precision, thus by utilizing high-speed continuous casting and nothing
The CEM technique of head rolling mode provides property and hole expandability uniform in material excellent precipitation strength type hot rolled steel plate, and completes this
Invention.
In the following, the precipitation strength type hot rolled steel plate excellent to property and hole expandability uniform in material according to an aspect of the present invention
It is described in detail.
The excellent precipitation strength type hot rolled steel plate of the property and hole expandability uniform in material of an aspect of of the present present invention, with weight %
Meter, comprising: C:0.02-0.05%；Si:0.01~0.3%；Mn:1.0~1.6%；Ti:0.04~0.1%；Nb:0.01~
0.05%；N:0.008% or less the and Fe of surplus and other inevitable impurity, and meet following formula (1), the steel plate
Microstructure include 95 area % or more ferrite and (Ti, Nb) C miscible precipitate, be formed by diameter be 10nm with
Under (Ti, Nb) C miscible precipitate quantity be diameter be more than five times or more of (Ti, Nb) C miscible precipitate quantity of 10nm.
Formula (1): 0.35≤(Ti+Nb+V+Mo)/(C+N)≤0.70
Wherein, in the formula (1), each element symbol indicates the atomicity percentage composition (at.%) of each element, does not include
Element in steel is calculated as 0.
Firstly, the conjunction of the excellent precipitation strength type hot rolled steel plate of property and hole expandability uniform in material to an aspect of of the present present invention
Gold composition is described in detail.Hereinafter, the unit of each element content is weight %.
C:0.02~0.05%
The C is the most economical and effective element for strengthening steel, still, when the C content is present in sub- peritectoid area
When (Hypo-Peritectic Composition), in the process of setting in high-speed casting, it will cause liquid and ferrite
It is changed into volume contraction phenomenon in the transition process of austenite (liquid+ferrite → austenite), and promotes the production of face crack
It is raw.
When C content is more than 0.05%, face crack can be generated during high-speed casting.On the other hand, when C content is small
When 0.02%, intensity and weldability can be significantly reduced.
Si:0.01~0.3%
Si is as the oxygen in removal molten steel and stablizes ferritic element, promotes iron element in cooling procedure after hot rolling
Body transformation, so as to form uniform ferritic structure, and facilitates to ensure high-intensitive material by solid solution strengthening effect.
When Si content is less than 0.01%, said effect is insufficient.On the other hand, when Si content is more than 0.3%, solid solution
Strengthening effect can be greater than precipitating reinforcing effect, and surface of steel plate forms the red oxidization skin as caused by Si when hot rolling, therefore can reduce
Surface of steel plate quality.It is highly preferred that the upper limit of Si content is 0.2%, much further preferably from 0.1%.
Mn:1.0~1.6%
Identical as Si, Mn is equally the effective element for Solid Solution Strengthened Steel.
When Mn content is less than 1.0%, according to the design of the C of above-mentioned addition low content, it is difficult to substantially ensure weld part
Intensity.On the other hand, when Mn content is more than 1.6%, ferritic transformation meeting excessive deferral cannot achieve and effect is adequately precipitated
Fruit, and interior formation carbide or pearlite are organized, edge processability is rushed in reduction, therefore the Mn content in the present invention is preferably limited to
1.0~1.6%.
Ti:0.04~0.1%
Ti is to be made when being changed into ferrite from austenite due to the fine precipitation effect of interphase interface (Ti, Nb) C by force
Degree rises maximized element.
When Ti content is less than 0.04%, due to the N for inevitably including in steel making technology be difficult to ensure adequately it is micro-
It is thin that effect is precipitated.On the other hand, when Ti content is more than 0.1%, fine precipitation effect saturation exists after forming nano-precipitation
Remaining Ti, thus it is economically not preferred.
Nb:0.01~0.05%
Nb is the important element that the fine precipitation of (Ti, Nb) C is formed together with Ti, and is for imperceptibly forming ferrite
The effective element of granularity.
When Nb content is less than 0.01%, it is difficult to realize said effect.On the other hand, when Nb content is greater than 0.05%,
The non-recrystallization region temperature of material rises, to can cause load problem when rolling.
N:0.008% or less
Even if there are minimal amount of N, the engineering properties of steel can also be produced a very large impact, and increase tensile strength and bend
Take intensity.But N can reduce elongation percentage, cause blue heat brittleness and reduce the impact characteristics of material, draw when especially thin plate is processed
Play the principal element that surface generates the strain-aging of fold.Also, nitrogen is in conjunction with other alloying elements and forms nitride, because
This, can reduce the important fine precipitation effect of (Ti, Nb) C in the present invention.
Therefore, N is equivalent to impurity in the present invention, it is preferable that its content is strict controlled in 0.008% or less.
Remaining ingredient of the invention is iron (Fe).It, can be from raw material or ambient enviroment not but in common manufacturing process
It is mixed into unexpected impurity avoidablely, it is thus impossible to exclude this impurity.The technical staff of general manufacturing process both knows about
These impurity, therefore these not specifically mentioned contents in the present invention.For example, can inevitably be mixed into P, S, Cu, V, Ni,
Al, Cr etc..
In the present invention, each element not only meets above-mentioned each element content, but also needs to meet following formula (1).
Formula (1): 0.35≤(Ti+Nb+V+Mo)/(C+N)≤0.70
Wherein, in the formula (1) each element symbol indicate each element atomicity percentage composition (at.%), be not included in
Element in steel is calculated as 0.
Meaning on the metallurgy of the formula (1) is to consider that the initial stage based on C, N is thick to maximize fine pick-up behavior
It is big that caused Ti, Nb, V, Mo loss is precipitated, confirm optimal atomic weight ratio.Such equivalent proportion, ability are only considered in advance
Enough minimize the content of the admittedly molten element such as Si, Cr, it is at low cost and rush the steel of edge excellent in workability to manufacture alloyed iron.
When the value of the formula (1) is less than 0.35, it is difficult to ensure sufficient (Ti, Nb) C miscible precipitate in ferrite, causes
Intensity material is unqualified.On the other hand, it when the value of the formula (1) is more than 0.70, is chemically combined and is formed with C according to equivalent proportion
After miscible precipitate remaining remaining Ti, Nb, V, Mo etc. act solely on intensity effect it is relatively small, and to ensure through
Ji property has a negative impact.
Also, each element not only meets each element content and formula (1) value, but also can meet following formula (2) value.
Formula (2): 0.04≤(Ti+Nb+V+Mo)/(C+Mn+Si+Cr)
Wherein, in the formula (2) each element symbol indicate each element atomicity percentage composition (at.%), be not included in
Element in steel is calculated as 0.
The formula (2) considers the atomic ratio that element ti, Nb, Mo, V and admittedly molten Elements C, Si, Mn, Cr is precipitated, be in order to
Ensure target tensile strength by precipitation strength.
When the value of the formula (2) is less than 0.04, the effect based on precipitation strength is less than the effect based on admittedly molten reinforcing, because
This needs to add a large amount of Si, Mn, Cr etc. and melts intensified element, manufacturing cost admittedly to meet the tensile strength of 590MPa or more
Rise.
The excellent precipitation strength type hot rolled steel plate of property and hole expandability uniform in material according to an aspect of the present invention it is fine
Tissue, ferrite and (Ti, Nb) C miscible precipitate including 95 area % or more, being formed by diameter is that 10nm is below
(Ti, Nb) C miscible precipitate quantity is that diameter is more than five times or more of (Ti, Nb) C miscible precipitate quantity of 10nm.The present invention
In, (Ti, Nb) C miscible precipitate refers to that, including TiC, NbC and (Ti, Nb) C double carbide, the diameter indicates that equivalent circle is straight
Diameter.
When ferrite is less than 95 area %, largely there is pearlite and low-temperature transformation is equal and ferritic phase is than alternate hardness
The big tissue of difference, therefore, it is difficult to ensure to rush edge processability.
Diameter is that 10nm (Ti, Nb) C miscible precipitate quantity below is compound less than (Ti, Nb) C that diameter is more than 10nm
At five times of precipitate quantity, precipitating reinforcing effect is insufficient, and tensile strength is deteriorated.
Diameter is that 10nm (Ti, Nb) C miscible precipitate quantity below is the compound analysis of (Ti, Nb) C that diameter is more than 10nm
It is 5 or more that five times or more of object quantity, which are the values of expression (3), out.
Formula (3):
In the formula (3), PN indicates the quantity of (Ti, Nb) C miscible precipitate in hot rolled steel plate tissue, and d expression passes through
The diameter of the miscible precipitate of scanning electron microscope (TEM) observation, and unit is nm.Diameter is respectively indicated to be more than 0 and 10nm or less, be more than
10nm and 20nm or less, more than 20nm and 50nm or less, more than the quantity of 50nm and 100nm precipitate below, more than 100nm
Precipitate there's almost no, therefore except.
At this point, the distance between described (Ti, Nb) C miscible precipitate can be 30nm or less.
More specifically, indicating to pass through scanning electron microscope on the basis of [001] or [110] crystal zone axis (Zone Axis)
(TEM) when observing tissue, with curve (Curve) or the interphase interface precipitate of straight line (Straight) morphologic arrangement
The line-spacing (Line-Spacing, LS) of (Interphase Precipitation) is 30nm or less.The compound precipitation of (Ti, Nb) C
It is fine that the significant effect reduction for acting on intensity is precipitated when distance is more than 30nm between object.For between (Ti, Nb) C miscible precipitate
The lower limit of distance is not particularly limited, and can be 5nm or more.
Also, (Ti, Nb) the C miscible precipitate can be 15000/μm2More than.
This is because even if distance meets 30nm hereinafter, when (Ti, Nb) C is compound between (Ti, Nb) the C miscible precipitate
Precipitate is less than 15000/μm2When, it also cannot achieve point of the uniform and fine precipitate in crystal grain on entire area
Cloth, to be difficult to ensure intensity and rush edge processability.
In addition, the tensile strength of hot rolled steel plate of the invention can be 590MPa or more, the material in width/height direction is inclined
Difference can be within ± 5% range compared to average value.It can not only ensure the materials deviation such as excellent intensity, elongation percentage as a result,
And it can ensure the material deviation of excellent hole expandability.
In the following, the excellent precipitation strength type hot rolled steel plate of property and hole expandability uniform in material to another aspect of the present invention
Manufacturing method is described in detail.
The manufacturer of the excellent precipitation strength type hot rolled steel plate of the property and hole expandability uniform in material of another aspect of the present invention
Method includes: continuous casting step, continuous casting is carried out to the molten steel for meeting above-mentioned composition of alloy, to manufacture sheet billet；Roughing step, to described
Sheet billet carries out roughing, to obtain bar steel (Bar)；Heating stepses carry out heating or concurrent heating to the bar steel；Finishing step, it is right
The bar steel of heating carries out finish to gauge, to obtain hot rolled steel plate；Cooling step, will on runout table (run out table)
The hot rolled steel plate is cooled to 600~700 DEG C with the cooling velocity of 30 DEG C/s or more, then carries out air-cooled；And winding step,
450~600 DEG C at a temperature of the cooling hot rolled steel plate is wound.
Continuous casting step
Continuous casting is carried out to the molten steel for meeting above-mentioned composition of alloy, to manufacture sheet billet.
At this point, the thickness of the sheet billet can be 30-150mm.By the company of sheet billet (thin slab) and conventional mill
The slab of casting machine 200mm or more produced is compared.The slab of past 200mm or more is completely cold in outdoor storage field etc.
But, it therefore needs that the surface temperature of slab is sufficiently again heated to 1100 DEG C or more in reheating furnace before carrying out hot rolling.But
It is that in the present invention, sheet billet is delivered directly to roughing mill without reheating furnace, therefore can be directly hot using continuous casting, from
And energy can be saved and greatly improve productivity.
Roughing step
Roughing is carried out to the sheet billet, to obtain bar steel.At this point, the roughing can at a temperature of 850~1150 DEG C into
Row.This is because being easy to crack in edge part when roughing temperature is less than 850 DEG C, when roughing temperature is more than 1150 DEG C
When, when rolling, is easy to crack on sheet billet surface.
Heating stepses
Heating or concurrent heating are carried out to the bar steel.At this point, can heat or the temperature range of concurrent heating to 850~1150 DEG C.When
When the temperature is less than 850 DEG C, biggish rolling load is generated in finish to gauge, when the temperature is more than 1150 DEG C, is not only used
Increase in the cost of energy of heating, and the tendency that surface scale defect occurs increases, therefore heating temperature is preferably controlled in
850~1150 DEG C.
At this point, to the institute that before subsequent finishing step can also further comprise winding heating after the heating stepses
The step of stating bar steel.
Finishing step
Finish to gauge is carried out to the bar steel of heating, to obtain hot rolled steel plate.At this point, the finish to gauge can be at 770~1000 DEG C
Within the temperature range of carry out.This is because two-phase section effect of rolling becomes strong, and due to extreme when finishing temperature is less than 770 DEG C
The anisotropy of tissue and be difficult to ensure required material.On the other hand, in order to by finishing temperature control greater than 1000 DEG C
Temperature needs to carry out in the heating stepses 1150 DEG C or more of high-temperature heating, and this can cause surface scale defect, warp
Ji higher cost.
Cooling step
The hot rolled steel plate is cooled to 600~700 DEG C with the cooling velocity of 30 DEG C/s or more on the run-out table, then
It carries out air-cooled.When cooling termination temperature is more than 600~700 DEG C of temperature ranges, it is unable to fully realize that austenite is changed into ferrite
When the fine pick-up behavior that generates.Also, even if meeting the cooling termination temperature, when cooling velocity is less than 30 DEG C/s,
The ferritic transformation that most of score can be realized before air-cooled section, for ensuring that the ferrite fraction of nano-precipitation significantly subtracts
It is few, to be unable to ensure target strength material.
At this point, the plate speed of hot rolled steel plate on the run-out table can be 100~200mpm, speed difference be can be
10% or less.
Wind step
450~600 DEG C at a temperature of the cooling hot rolled steel plate is wound.Less than 450 DEG C at a temperature of
When being wound, it is difficult to control uniform temperature due to entering boiling transition section.Also, cause martensite and bainite etc.
Hard phase is mixed into, and rushes edge processability so as to significantly reduce.On the other hand, more than 600 DEG C at a temperature of wound when,
Another hard phase such as cementite is formed, rushes edge processability to can reduce.
Specific embodiment
In the following, more specifically being illustrated by embodiment to the present invention.But following embodiment is only to be considered illustrative
And the present invention is illustrated, do not limit interest field of the invention.This is because interest field of the invention is wanted by right
It asks the item recorded in book and the item thus rationally derived and determines.
Prepare have following table 1 in indicate at the molten steel being grouped as.
Other than comparative example 5,6 and 7, remaining is manufactured in the following manner hot rolled steel plate, that is, uses CEM technique, and leads to
High-speed casting is crossed to carry out roughing at a temperature of 1000 DEG C after manufacturing the sheet billet with a thickness of 90mm, without being cooled to room temperature, and
The finishing temperature (FDT) recorded in following table 2 executes finish to gauge, and the cooling velocity and plate speed recorded in following table 2 are cooled to
It 650 DEG C, then carries out air-cooled, and is wound at the winding temperature (CT) recorded in the following table 2, thus manufacture hot rolled steel plate.
Comparative example 5,6 and 7 is manufactured in the following manner hot rolled steel plate, that is, using conventional mill mode manufacture with a thickness of
The slab of 220mm, and (1250 DEG C) and roughing (1000 DEG C) are reheated after being cooled to room temperature, the end recorded in following table 2
It rolls temperature (FDT) and executes finish to gauge, while the cooling velocity and plate speed recorded in following table 2 are cooled to 650 DEG C, then carry out
It is air-cooled, and wound at the winding temperature (CT) recorded in the following table 2, thus manufacture hot rolled steel plate.
Precipitate quantity, formula (3) value, property uniform in material, expansion of the hot rolled steel plate of each size manufactured by measurement or evaluation
It is documented in the following table 3 after permeability, tensile strength (TS), fracture elongation (EI) and ferrite fraction.
Tension test is on the basis of 90 ° of directions of the rolling direction relative to rolled plate, to according to JIS-5 specification
The test piece of acquirement is tested.Ferritic phase score is accordingly to be rolled using Nital etching solution and the etching of LePera etching solution respectively
Then panel test piece is observed under 500 amplification factors with optical microscopy and is analyzed, compared with image (Image) analyzer
It obtains afterwards.
Hole expandability evaluation is to be existed after preparing the square test piece that horizontal and vertical size is respectively 120mm by punching operation
Test piece is centrally formed the hole that diameter is 10mm, then lifts burr (burr) and is boosted using cone, and until in circumference
The value that the percentage of bore dia and the ratio between initial hole diameter (10mm) that part is expanded before cracking calculates.
In order to be confirmed whether to ensure simultaneously that the material of the materials such as excellent intensity, elongation percentage deviation and hole expandability is inclined
Difference measures the material deviation of the hole expandability in width/height direction, when the material deviation phase of the hole expandability in width/height direction
Than average value when within ± 5% range, it is expressed as well, being expressed as when being more than ± 5% range bad.
Sludge Analysis is using TEM on the basis of Zone Axis [100] in 1400000nm2Hot-rolled steel is observed in area
Board group knits interior precipitate, and the interphase interface precipitate (Interphase of curve or rectilinear configuration can be mainly observed along 331 faces
Precipitation)。
Formula (3):
PN indicates the quantity of (Ti, Nb) C miscible precipitate in hot rolled steel plate tissue in the formula (3), and d expression passes through
The diameter of the miscible precipitate of scanning electron microscope (TEM) observation, and unit is nm.Diameter is respectively indicated to be more than 0 and 10nm or less, be more than
10nm and 20nm or less, more than 20nm and 50nm or less, more than the quantity of 50nm and 100nm precipitate below, in following table 3
It is middle to be indicated respectively with PN10, PN20, PN50, PN100.
[table 1]
| It distinguishes | C | Si | Mn | Nb | Ti | N | Formula (1) | Formula (2) |
| Comparative example 1 | 0.038 | 0.060 | 1.435 | 0.014 | 0.045 | 0.008 | 0.292 | 0.039 |
| Comparative example 2 | 0.044 | 0.064 | 1.447 | 0.014 | 0.049 | 0.008 | 0.277 | 0.041 |
| Comparative example 3 | 0.050 | 0.059 | 1.403 | 0.003 | 0.067 | 0.008 | 0.302 | 0.052 |
| Comparative example 4 | 0.040 | 0.088 | 1.429 | 0.005 | 0.055 | 0.007 | 0.314 | 0.041 |
| Comparative example 5 | 0.030 | 0.050 | 1.400 | 0.010 | 0.070 | 0.004 | 0.564 | 0.058 |
| Comparative example 6 | 0.045 | 0.060 | 1.400 | 0.011 | 0.075 | 0.006 | 0.404 | 0.061 |
| Comparative example 7 | 0.050 | 0.065 | 1.500 | 0.010 | 0.100 | 0.006 | 0.455 | 0.071 |
| Comparative example 8 | 0.030 | 0.050 | 1.400 | 0.010 | 0.070 | 0.004 | 0.564 | 0.058 |
| Example 1 | 0.049 | 0.069 | 1.427 | 0.014 | 0.076 | 0.007 | 0.360 | 0.061 |
| Example 2 | 0.046 | 0.067 | 1.418 | 0.014 | 0.066 | 0.007 | 0.391 | 0.054 |
| Example 3 | 0.049 | 0.077 | 1.416 | 0.011 | 0.077 | 0.007 | 0.377 | 0.061 |
| Example 4 | 0.043 | 0.080 | 1.553 | 0.013 | 0.081 | 0.006 | 0.457 | 0.059 |
| Example 5 | 0.030 | 0.050 | 1.400 | 0.010 | 0.070 | 0.004 | 0.564 | 0.058 |
| Example 6 | 0.044 | 0.061 | 1.472 | 0.011 | 0.075 | 0.006 | 0.412 | 0.058 |
| Example 7 | 0.030 | 0.050 | 1.400 | 0.010 | 0.085 | 0.006 | 0.644 | 0.069 |
In the table 1, the unit of each element content is weight %, and formula (1) and formula (2) are as follows.
Formula (1): 0.35≤(Ti+Nb+V+Mo)/(C+N)≤0.70
Formula (2): 0.04≤(Ti+Nb+V+Mo)/(C+Mn+Si+Cr)
Wherein, each element symbol indicates the atomicity percentage composition (at.%) of each element in the formula (1) and formula (2), no
0 is calculated as including the element in steel.
[table 2]
[table 3]
It can be confirmed and meet the examples 1 of all conditions proposed by the present invention to the property uniform in material of example 7 and reaming
Property is excellent, and can ensure the tensile strength of 590MPa or more.
On the other hand, although although confirming each element content of comparative example 1 and 2 in effective range proposed by the present invention
It is interior, it is unsatisfactory for formula (1) value, comparative example 3 and 4 is the case where being unsatisfactory for Nb content and formula (1) value, although hole expandability is excellent, but
It cannot achieve sufficient precipitating reinforcing effect, tensile strength is low.
The case where comparative example 5,6 and 7 is using conventional mill mode, although it is excellent to confirm tensile strength, material
Uniformity is poor.
Comparative example 5,8 and example 5 are the situations that composition of alloy is identical but manufacturing condition is different, confirm comparative example 5
Using general rolling mill technology, property uniform in material is poor, and the cooling velocity of comparative example 8 is low and tensile strength is poor, but the material of example 5
Uniformity and tensile strength are excellent.
Fig. 1, Fig. 2 and Fig. 3 are respectively example 1, comparative example 1 and the comparative example 7 shot by scanning electron microscope
The photo of microstructure.When compared with Fig. 2 and Fig. 3, can from Fig. 1 confirm example 1 in form it is fine and uniform (Ti,
Nb) C miscible precipitate.
It is illustrated above by reference to embodiment, the thought and field of the invention recorded in not departing from claims
In range, those of ordinary skill in the art are able to carry out a variety of modification and deformation.
Claims (13)
1. a kind of property uniform in material and the excellent precipitation strength type hot rolled steel plate of hole expandability, in terms of weight %, comprising: C:
0.02-0.05%；Si:0.01~0.3%；Mn:1.0~1.6%；Ti:0.04~0.1%；Nb:0.01~0.05%；N:
0.008% or less and surplus Fe and other inevitable impurity, and meet following formula (1),
The microstructure of the hot rolled steel plate includes the ferrite and (Ti, Nb) C miscible precipitate of 95 area % or more, institute's shape
At diameter be 10nm (Ti, Nb) C miscible precipitate quantity below be (Ti, Nb) C miscible precipitate that diameter is more than 10nm
Five times or more of quantity,
Formula (1): 0.35≤(Ti+Nb+V+Mo)/(C+N)≤0.70
Wherein, in the formula (1), each element symbol indicates the atomicity percentage composition (at.%) of each element, is not included in steel
In element be calculated as 0.
2. property uniform in material according to claim 1 and the excellent precipitation strength type hot rolled steel plate of hole expandability, feature exist
In,
The hot rolled steel plate meets following formula (2),
Formula (2): 0.04≤(Ti+Nb+V+Mo)/(C+Mn+Si+Cr)
Wherein, in the formula (2) each element symbol indicate each element atomicity percentage composition (at.%), be not included in steel
Element be calculated as 0.
3. property uniform in material according to claim 1 and the excellent precipitation strength type hot rolled steel plate of hole expandability, feature exist
In,
The distance between described (Ti, Nb) C miscible precipitate is 30nm or less.
4. property uniform in material according to claim 1 and the excellent precipitation strength type hot rolled steel plate of hole expandability, feature exist
In,
(Ti, Nb) the C miscible precipitate is 15000/μm2More than.
5. property uniform in material according to claim 1 and the excellent precipitation strength type hot rolled steel plate of hole expandability, feature exist
In,
The tensile strength of the hot rolled steel plate is 590MPa or more, the material deviation in width/height direction compared to average value ±
Within 5% range.
6. the manufacturing method of a kind of property uniform in material and the excellent precipitation strength type hot rolled steel plate of hole expandability, comprising:
Continuous casting step carries out continuous casting to molten steel, and to manufacture sheet billet, the molten steel is in terms of weight %, comprising: C:0.02-
0.05%；Si:0.01~0.3%；Mn:1.0~1.6%；Ti:0.04~0.1%；Nb:0.01~0.05%；N:0.008%
Below and the Fe of surplus and other inevitable impurity, and meet following formula (1)；
Roughing step carries out roughing to the sheet billet, to obtain bar steel；
Heating stepses carry out heating or concurrent heating to the bar steel；
Finishing step carries out finish to gauge to the bar steel of heating, to obtain hot rolled steel plate；
The hot rolled steel plate is cooled to 600~700 on the run-out table with the cooling velocity of 30 DEG C/s or more by cooling step
DEG C, it then carries out air-cooled；And
Wind step, 450~600 DEG C at a temperature of the cooling hot rolled steel plate is wound,
Formula (1): 0.35≤(Ti+Nb+V+Mo)/(C+N)≤0.70
Wherein, in the formula (1), each element symbol indicates the atomicity percentage composition (at.%) of each element, is not included in steel
In element be calculated as 0.
7. the manufacturer of property uniform in material according to claim 6 and the excellent precipitation strength type hot rolled steel plate of hole expandability
Method, which is characterized in that
The molten steel meets following formula (2),
Formula (2): 0.04≤(Ti+Nb+V+Mo)/(C+Mn+Si+Cr)
Wherein, in the formula (2) each element symbol indicate each element atomicity percentage composition (at.%), be not included in steel
Element be calculated as 0.
8. the manufacturer of property uniform in material according to claim 6 and the excellent precipitation strength type hot rolled steel plate of hole expandability
Method, which is characterized in that
The sheet billet with a thickness of 30~150mm.
9. the manufacturer of property uniform in material according to claim 6 and the excellent precipitation strength type hot rolled steel plate of hole expandability
Method, which is characterized in that
The plate speed of hot rolled steel plate on the run-out table is 100~200mpm, and speed difference is 10% or less.
10. the manufacturer of property uniform in material according to claim 6 and the excellent precipitation strength type hot rolled steel plate of hole expandability
Method, which is characterized in that
It further comprise the step of winding the bar steel of heating between the heating stepses and the finishing step.
11. the manufacturer of property uniform in material according to claim 6 and the excellent precipitation strength type hot rolled steel plate of hole expandability
Method, which is characterized in that
The roughing carries out within the temperature range of 850~1150 DEG C.
12. the manufacturer of property uniform in material according to claim 6 and the excellent precipitation strength type hot rolled steel plate of hole expandability
Method, which is characterized in that
In the heating stepses, the bar steel is heated or the temperature range of concurrent heating to 850~1150 DEG C.
13. the manufacturer of property uniform in material according to claim 6 and the excellent precipitation strength type hot rolled steel plate of hole expandability
Method, which is characterized in that
The finish to gauge carries out within the temperature range of 770~1000 DEG C.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR10-2016-0078573 | 2016-06-23 | ||
| KR1020160078573A KR101767839B1 (en) | 2016-06-23 | 2016-06-23 | Precipitation-hardening hot-rolled steel sheet having excellent uniformity and hole expansion and method for manufacturing the same |
| PCT/KR2017/006668 WO2017222343A1 (en) | 2016-06-23 | 2017-06-23 | Precipitation-hardening hot rolled steel sheet having excellent material uniformity and hole expandability, and manufacturing method therefor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN109415791A true CN109415791A (en) | 2019-03-01 |
Family
ID=60142108
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201780037469.4A Withdrawn CN109415791A (en) | 2016-06-23 | 2017-06-23 | Property and hole expandability uniform in material excellent precipitation strength type hot rolled steel plate and its manufacturing method |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US20200325563A1 (en) |
| EP (1) | EP3476969A4 (en) |
| KR (1) | KR101767839B1 (en) |
| CN (1) | CN109415791A (en) |
| WO (1) | WO2017222343A1 (en) |
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| JP2000087142A (en) * | 1998-09-10 | 2000-03-28 | Nkk Corp | Production of high tensile hot rolled steel strip having ferritic and bainitic structure |
| CN101646794A (en) * | 2007-03-27 | 2010-02-10 | 新日本制铁株式会社 | High-strength hot rolled steel sheet being free from peeling and excelling in surface and burring properties and process for manufacturing the same |
| EP2743364A1 (en) * | 2011-08-09 | 2014-06-18 | Nippon Steel & Sumitomo Metal Corporation | Hot-rolled steel sheet having high yield ratio and excellent low-temperature impact energy absorption and haz softening resistance and method for producing same |
| KR20140081048A (en) * | 2012-12-21 | 2014-07-01 | 주식회사 포스코 | Hot rolled with excellent hole expansion and variation of mechanical properties and method for manufacturing the same |
| KR20140085188A (en) * | 2012-12-27 | 2014-07-07 | 주식회사 포스코 | Method for manufacturing hot rolled steel plate and hot rolled steel sheet |
| KR20150025910A (en) * | 2013-08-30 | 2015-03-11 | 현대제철 주식회사 | High strength hot-rolled steel sheet and method of manufacturing the same |
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| KR100711481B1 (en) | 2005-12-26 | 2007-04-24 | 주식회사 포스코 | A method for manufacturing hot rolled steel sheet for automobile having excellent property of precipitation hardening |
| CN101538680A (en) * | 2009-05-06 | 2009-09-23 | 湖南华菱涟源钢铁有限公司 | Method for producing high-strength steel with yield strength of 600MPa level |
| KR101245699B1 (en) | 2010-11-10 | 2013-03-25 | 주식회사 포스코 | METHOD FOR MANUFACTURING TENSILE STRENGTH 590MPa CLASS HOT ROLLED TRIP STEEL WITH EXCELLENT VARIATION OF MECHANICAL PROPERTY |
| KR101245701B1 (en) | 2010-11-15 | 2013-04-01 | 주식회사 포스코 | METHOD FOR MANUFACTURING TENSILE STRENGTH 590MPa CLASS HOT ROLLED DP STEEL WITH EXCELLENT WORKABILITY AND VARIATION OF MECHANICAL PROPERTY |
-
2016
- 2016-06-23 KR KR1020160078573A patent/KR101767839B1/en active IP Right Grant
-
2017
- 2017-06-23 EP EP17815756.6A patent/EP3476969A4/en not_active Withdrawn
- 2017-06-23 WO PCT/KR2017/006668 patent/WO2017222343A1/en unknown
- 2017-06-23 US US16/305,603 patent/US20200325563A1/en not_active Abandoned
- 2017-06-23 CN CN201780037469.4A patent/CN109415791A/en not_active Withdrawn
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|---|---|---|---|---|
| JPH07224324A (en) * | 1994-02-09 | 1995-08-22 | Nisshin Steel Co Ltd | Production of high strength steel plate for precision punching |
| JP2000087142A (en) * | 1998-09-10 | 2000-03-28 | Nkk Corp | Production of high tensile hot rolled steel strip having ferritic and bainitic structure |
| CN101646794A (en) * | 2007-03-27 | 2010-02-10 | 新日本制铁株式会社 | High-strength hot rolled steel sheet being free from peeling and excelling in surface and burring properties and process for manufacturing the same |
| EP2743364A1 (en) * | 2011-08-09 | 2014-06-18 | Nippon Steel & Sumitomo Metal Corporation | Hot-rolled steel sheet having high yield ratio and excellent low-temperature impact energy absorption and haz softening resistance and method for producing same |
| KR20140081048A (en) * | 2012-12-21 | 2014-07-01 | 주식회사 포스코 | Hot rolled with excellent hole expansion and variation of mechanical properties and method for manufacturing the same |
| KR20140085188A (en) * | 2012-12-27 | 2014-07-07 | 주식회사 포스코 | Method for manufacturing hot rolled steel plate and hot rolled steel sheet |
| KR20150025910A (en) * | 2013-08-30 | 2015-03-11 | 현대제철 주식회사 | High strength hot-rolled steel sheet and method of manufacturing the same |
Also Published As
| Publication number | Publication date |
|---|---|
| US20200325563A1 (en) | 2020-10-15 |
| EP3476969A1 (en) | 2019-05-01 |
| EP3476969A4 (en) | 2019-06-12 |
| WO2017222343A1 (en) | 2017-12-28 |
| KR101767839B1 (en) | 2017-08-14 |
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