CN109328240A - The high-strength steel sheet and its manufacturing method of low yield strength ratio characteristic and excellent in low temperature toughness - Google Patents
The high-strength steel sheet and its manufacturing method of low yield strength ratio characteristic and excellent in low temperature toughness Download PDFInfo
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- CN109328240A CN109328240A CN201780039727.2A CN201780039727A CN109328240A CN 109328240 A CN109328240 A CN 109328240A CN 201780039727 A CN201780039727 A CN 201780039727A CN 109328240 A CN109328240 A CN 109328240A
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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
- 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
- C21D1/26—Methods of annealing
- C21D1/28—Normalising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C—CHEMISTRY; METALLURGY
- 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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- 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
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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
- C21D2211/001—Austenite
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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Abstract
One aspect of the present invention is related to the high-strength steel sheet of a kind of low yield strength ratio characteristic and excellent in low temperature toughness, it includes 0.03%~0.08% C in terms of weight %, 0.05%~0.3% Si, 1.0%~2.0% Mn, 0.005%~0.04% Al, 0.005%~0.04% Nb, 0.001%~0.02% Ti, 0.05%~0.4% Cu, 0.6%~2.0% Ni, 0.08%~0.3% Mo, 0.002%~0.006% N, P less than or equal to 0.01%, S less than or equal to 0.003%, the Fe of surplus and inevitable impurity, microscopic structure includes 80%~92% ferrite in terms of area fraction, 8%~20% The average-size according to equivalent diameter measurement of MA (martensite/austenite line and staff control), the MA are less than or equal to 3 μm.
Description
Technical field
The present invention relates to the high-strength steel sheets and its manufacturing method of a kind of low yield strength ratio characteristic and excellent in low temperature toughness.
Background technique
In order to be not only used as shipbuilding, ocean structure body steel, and it is applied to require the industry of molding and shatter-proof characteristic
Field, needing to develop not only has ultralow-temperature flexibility, but also the steel with low yield strength ratio characteristic.
Steel with low yield strength ratio not only can have excellent by increasing the difference of yield strength and tensile strength
Different mouldability, and plastic deformation time point until can destroy can be postponed, energy is absorbed in the process
Amount, to prevent avalanche caused by external force.In addition, even if exist deformation, can also be repaired before avalanche, so as to prevent
Only life and property loss caused by the destruction of works.
In order to ensure low yield strength ratio, a kind of technology for making steel that there is two-phase structure is had developed.Specifically, the first phase is
It is made of soft ferritic, and remaining second phase is made of martensite, pearlite or bainite, to realize low bend by force
Than.
However, leading to impact toughness decreased there are lightweight two-phase and in order to which the second phase carbon content increase causes weld part tough
Property be deteriorated and the problem of cause the brittle break of works at low temperature.
Therefore, patent document 1 has been gone out as the technological development for ensuring low yield strength ratio and low-temperature impact toughness.
In patent document 1, by making MA of the microscopic structure comprising 2 volume of volume %~10 %, (martensite/austenite is mixed
Be combined and knit) and the acicular ferrite of 90 volume % or more ensure low yield strength ratio and excellent low-temperature flexibility.
According to patent document 1, about 0.8 or so yield tensile ratio may be implemented, but can not achieve sufficient low yield strength ratio, it is insufficient
To ensure shatter-proof characteristic.
Therefore, it is necessary to develop a kind of height of low yield strength ratio characteristic and excellent in low temperature toughness that can ensure that lower yield tensile ratio
Strength steel sheet and its manufacturing method.
(citation)
(patent document 1): Korean Patent Publication bulletin the 2013-0076577th
Summary of the invention
Technical problem
One aspect of the present invention provides high-strength steel sheet and its manufacturer of a kind of low yield strength ratio characteristic and excellent in low temperature toughness
Method.
In addition, the technical problems to be solved by the invention are not limited to above content, it can be based on the entire content of this specification
Understand the technical problems to be solved by the invention, for those skilled in the art, understands this hair
Bright supplementary technology problem does not have hell and high water.
Technical solution
One aspect of the present invention provides the high-strength steel sheet of a kind of low yield strength ratio characteristic and excellent in low temperature toughness, with weight %
Meter comprising 0.03%~0.08% C, 0.05%~0.3% Si, 1.0%~2.0% Mn, 0.005%~0.04%
Al, 0.005%~0.04% Nb, 0.001%~0.02% Ti, 0.05%~0.4% Cu, 0.6%~2.0%
Ni, 0.08%~0.3% Mo, 0.002%~0.006% N, the P less than or equal to 0.01%, it is less than or equal to
0.003% S, the Fe of surplus and inevitable impurity, iron of the microscopic structure in terms of area fraction comprising 80%~92% are plain
Body, 8%~20% MA (martensite/austenite line and staff control), the MA according to equivalent diameter measure average-size
Less than or equal to 3 μm.
In addition, another aspect of the present invention provides a kind of system of the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness
The method of making includes:
The step of by heating of plate blank to 1050 DEG C~1200 DEG C, the slab include 0.03%~0.08% in terms of weight %
C, 0.05%~0.3% Si, 1.0%~2.0% Mn, 0.005%~0.04% Al, 0.005%~0.04%
Nb, 0.001%~0.02% Ti, 0.05%~0.4% Cu, 0.6%~2.0% Ni, 0.08%~0.3% Mo,
0.002%~0.006% N, the P less than or equal to 0.01%, the S less than or equal to 0.003%, surplus Fe and can not keep away
The impurity exempted from;
Be hot-rolled down to finish to gauge to the slab after the heating and terminate temperature and is 760 DEG C~850 DEG C and obtains hot rolled steel plate
The step of;
The step of hot rolled steel plate is cooled to the cooling velocity more than or equal to 5 DEG C/s less than or equal to 450 DEG C;And
The hot rolled steel plate after cooling is heated to keep after 850 DEG C~960 DEG C of temperature range [1.3t+ (10~
30)] the normalizing heat treatment step of minute.
The t is the value determined as unit of mm to the thickness of hot rolled steel plate.
In addition, above-mentioned technical proposal and unlisted whole features of the invention.Referring to following specific embodiments
It is more fully understood various features of the invention and thus bring advantage and effect.
Invention effect
According to the present invention it is possible to ensure excellent low yield strength ratio characteristic and low-temperature flexibility, it is particularly possible to ensure to be less than or wait
It in 0.65 low yield strength ratio, therefore not only may insure mouldability, but also may insure excellent shatter-proof characteristic.
It can be applied not only to shipbuilding, ocean structure body steel field as a result, can also be formed applied to requirement and resistance to
Shake the industrial field of characteristic.
Detailed description of the invention
Fig. 1 is to utilize the micro- of optical microscopy (Optical microscope, OM) shooting example, that is, test number 1
The photo of tissue.
Fig. 2 is to be using scanning electron microscope (Scanning electron microscope, SEM) shooting example
The photo of the microscopic structure of test number 1.
Fig. 3 is to utilize the aobvious of optical microscopy (Optical microscope, OM) shooting comparative example, that is, test number 12
The photo of micro-assembly robot.
Specific embodiment
The preferred embodiment of the present invention is described below.However, the present invention can deformation implementation in a variety of different ways, this
The range of invention is not limited to following embodiments.In addition, the purpose that embodiments of the present invention are provided below is to fields
Those of ordinary skill the present invention is described in more detail below.
Present inventors understand that the yield tensile ratio that may insure 0.8 or so by the prior art, so as to ensure certain journey
The mouldability of degree, but can not achieve sufficient low yield strength ratio, therefore be insufficient to assure that shatter-proof characteristic.It is asked to solve these
Topic, present inventor has performed further investigations.
The inventors discovered that, in order to realize low yield strength ratio, the bigger base material and the difference of hardness of the second phase the more advantageous after study
And the more uniform the distribution of MA the more advantageous, and the base material of patent document 1 is acicular ferrite, MA insufficient with the difference of hardness of MA
It is mutually formed in crystal boundary, MA size is coarse, therefore can not achieve sufficient low yield strength ratio.
It thereby confirms that, by forming the microscopic structure of base material by ferrite and fine MA phase being made to be evenly distributed in iron
Ferritic crystal boundary and intra-die, it can be ensured that the low yield strength ratio less than or equal to 0.65 needs to control in order to ensure such tissue
Tissue before normalizing heat treatment is made includes bainite, so as to complete the present invention.
The high intensity of low yield strength ratio characteristic and excellent in low temperature toughness according to an aspect of the present invention is described below in detail
Steel plate.
The high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness according to an aspect of the present invention, with weight
Measure % meter comprising 0.03%~0.08% C, 0.05%~0.3% Si, 1.0%~2.0% Mn, 0.005%~
0.04% Al, 0.005%~0.04% Nb, 0.001%~0.02% Ti, 0.05%~0.4% Cu, 0.6%~
2.0% Ni, 0.08%~0.3% Mo, 0.002%~0.006% N, the P less than or equal to 0.01%, it is less than or waits
In 0.003% S, the Fe of surplus and inevitable impurity, microscopic structure includes 80%~92% iron in terms of area fraction
Ferritic, 8%~20% MA (martensite/austenite line and staff control), the MA according to equivalent diameter measure average ruler
It is very little to be less than or equal to 3 μm.
Firstly, to the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness according to an aspect of the present invention
Alloy compositions are described in detail.The unit of each constituent content is weight % below.
C:0.03%~0.08%
In the present invention, C is the element for causing solution strengthening, and to be existed based on the carbonitride form of Nb etc., with
Ensure tensile strength.
If C content, less than 0.03%, above-mentioned effect is insufficient.On the contrary, if C content is greater than 0.08%,
MA becomes thick, and generates pearlite, it is possible to cause the impact characteristics under low temperature to be deteriorated, it is difficult to substantially ensure bainite.
Si:0.05%~0.3%
Si is to assist Al to make the element of deoxidation of molten steel, and Si is added in order to ensure yield strength and tensile strength.
If Si content, less than 0.05%, above-mentioned effect is insufficient.On the contrary, if Si content is greater than 0.3%,
Due to the coarsening of MA, it is possible to impact characteristics be caused to be deteriorated, it is also possible to welding characteristic be caused to decline.
Mn:1.0%~2.0%
Mn is to increase effect to the intensity based on solution strengthening to make the element of major contribution, and contribute to form bayesian
Body.
If Mn content, less than 1.0%, above-mentioned effect is insufficient.On the contrary, if excessive be added Mn, due to shape
It is segregated at MnS field trash and central part, it is possible to cause toughness to decline, therefore the upper limit is set as 2.0%.
Al:0.005%~0.04%
Main deoxidier of the Al as steel needs to be added more than or equal to 0.005%.But if additional amount is greater than
0.04%, then the effect can be saturated, and due to Al2O3The score of field trash, size increase, it is possible to become under low-temperature flexibility
The reason of drop.
Nb:0.005%~0.04%
Nb is that the recrystallization in rolling or cooling is inhibited to make structure refinement, increase by force by being dissolved or being precipitated carbonitride
The element of degree.If Nb content, less than 0.005%, above-mentioned effect is insufficient.On the contrary, if Nb content is greater than
0.04%, then there are problems that toughness declines after may result in base metal tenacity and welding.
Ti:0.001%~0.02%
Ti inhibits the coarsening of tissue by forming precipitate in conjunction with oxygen or nitrogen, makes to play to structure refinement
Contribution and the effect for improving toughness.
If Ti content, less than 0.001%, above-mentioned effect is insufficient.On the contrary, if Ti content is greater than 0.02%,
Then form coarse precipitate, it is possible to the reason of as damaging.
Cu:0.05%~0.4%
Cu is as the ingredient that not will lead to impact characteristics and be greatly reduced, by being dissolved and separating out raising intensity.In order to fill
Divide ground to improve intensity, needs comprising the Cu more than or equal to 0.05%, but if Cu content is greater than 0.4%, it is possible to it produces
Surface of steel plate crackle caused by the thermal shock of raw Cu.
Ni:0.6%~2.0%
Ni is the element that can improve intensity and toughness simultaneously, but intensity will not substantially be mentioned with the increase of Ni content
Height, and Ni is the element for reducing Ar3 temperature and contributing to form bainite.
If Ni content, less than 0.6%, above-mentioned effect is insufficient.On the contrary, if Ni content is greater than 2.0%,
Manufacturing cost increases, it is possible to weldability be caused to be deteriorated.
Mo:0.08%~0.3%
Mo is austenite stabilizer element, is had an impact to the increase of MA amount, and has great role to intensity is improved.This
Outside, Mo is the element that intensity declines and contribute to form bainite during preventing from being heat-treated.
If Mo content, less than 0.08%, above-mentioned effect is insufficient.On the contrary, if Mo content is greater than 0.3%,
Manufacturing cost increases, it is also possible to toughness after base metal tenacity and welding be caused to decline.
N:0.002%~0.006%
N is to make austenite structure refinement help to mention in heating of plate blank by being formed together precipitate with Ti, Nb, Al etc.
High-intensitive and toughness element.
If N content, less than 0.002%, above-mentioned effect is insufficient.On the contrary, if N content is greater than 0.006%,
It then will lead to face crack at high temperature and form precipitate, and remaining N exists with state of atom, it is possible to it reduces tough
Property.
P: less than or be equal to 0.01%
P is as impurity, it is possible to the reason of as causing cyrystal boundary segregation that steel is caused to become fragile.Therefore, very to the control of the upper limit
It is important, it is preferably controlled to be less than or equal to 0.01%.
S: less than or be equal to 0.003%
S forms MnS field trash as impurity, mainly in conjunction with Mn, these field trashes can become damage low-temperature flexibility because
Element.Therefore, critically important to the control of the upper limit, in order to ensure low-temperature flexibility, preferably the control of S content is being less than or equal to
0.003%.
Surplus ingredient of the invention is iron (Fe).But it can be inevitably mixed into from raw material in conventional manufacturing process
Or the unexpected impurity of ambient enviroment, therefore cannot exclude and be mixed into impurity.These impurity are the technologies of conventional manufacturing process
Anyone impurity for both knowing about of personnel, therefore repeated no more in relevant all the elements this specification.
The following detailed description of the high intensity of low yield strength ratio characteristic and excellent in low temperature toughness according to an aspect of the present invention
The microscopic structure of steel plate.
Micro- group of the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness according to an aspect of the present invention
Knit, in terms of area fraction include 80%~92% ferrite, 8%~20% MA, the MA according to equivalent diameter
The average-size of measurement is less than or equal to 3 μm.In the case where no specifically mentioned, below the score of microscopic structure refer to area
Score.
Ferrite is for ensuring that the phase of basic toughness and intensity, preferably greater than or equal to 80%.In addition, in order to ensure
Sufficient MA, the upper limit of ferrite fraction are preferably 92%.Further, the ferrite does not preferably include acicular ferrite.
This is because the difference of hardness of acicular ferrite and MA are small, it is unable to ensure sufficient low yield strength ratio.
If MA less than 8%, is difficult to ensure the low yield strength ratio less than or equal to 0.65, if MA is greater than 20%, rush
Hitting toughness may decline, and elongation percentage may reduce.In addition, if the average ruler of MA measured according to equivalent diameter
Very little to be greater than 3 μm, then MA is mainly formed at crystal boundary, it is difficult to ensure MA be uniformly distributed and low yield strength ratio.
Other than above-mentioned ferrite and MA, it may include other inevitable phases, this is not precluded outside.Than
Such as, it may include the pearlite less than or equal to 1 area %.
In the case, in order to ensure excellent low yield strength ratio characteristic and low-temperature flexibility, not only MA score and size will expire
The above-mentioned range of foot, and when drawing 100 μm of straight lines on steel plate of the invention, preferably there are 5~13 on the straight line
MA。
That is, on the microstructure picture having a size of 100 μm of 100 μ m vertically or left and right draw several it is straight
Line averagely may exist 5~13 MA at this time on each straight line.This is because the MA destroyed is mainly caused to be to be present in crystalline substance
The MA on boundary, when the condition is fulfilled, MA are evenly distributed in crystal boundary and intra-die, therefore it is advantageously ensured that low yield strength ratio.
Ratio additionally, there are the MA inside ferrite crystal grain and the MA for being present in crystal boundary can be 1:3~1:10.It is described
Ratio refers to the ratio of MA quantity, by meeting the ratio, the MA being present in inside ferrite crystal grain can be made equably to divide
Cloth is at 0.5 area of area %~5 %.
In addition, the ferritic average-size according to equivalent diameter measurement may be less than or equal to 20 μm.This be because
To be difficult to ensure sufficient toughness and intensity if ferritic average-size is greater than 20 μm.
In addition, steel plate according to the present invention is the steel plate being heat-treated by normalizing, the normalizing heat treatment front spring is shown
The bainite of micro-assembly robot can be 50 area of area %~90 %.
By making the microscopic structure of heat treatment front spring by inside, there are the bainites of carbide to form, and can be heat-treated
After so that MA is distributed evenly in crystal boundary and intra-die, therefore the bainite for being heat-treated the microscopic structure of front spring is preferably 50 faces
The product area of %~90 %.
In addition, the yield tensile ratio of steel plate according to the present invention can be 0.5~0.65, the low-temperature impact property at -40 DEG C can
More than or equal to 100J.Yield tensile ratio is less than or equal to 0.65, by increasing the difference of yield strength and tensile strength, can not only have
There is excellent mouldability, and plastic deformation time point until can destroy can be postponed, inhales in the process
Energy is received, to prevent avalanche caused by external force.
Therefore, shipbuilding, ocean structure body steel field be can be applied not only to, can also be preferably applied to require molding
With the industrial field of shatter-proof characteristic.
In the case, the yield strength of the steel plate can be 350MPa~400MPa, and tensile strength can be greater than or equal to
600MPa。
The high-strength of low yield strength ratio characteristic according to another aspect of the present invention and excellent in low temperature toughness is described below in detail
Spend the manufacturing method of steel plate.
The manufacture of the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness according to another aspect of the present invention
Method includes: will have the step of heating of plate blank of above-mentioned alloy compositions is to 1050 DEG C~1200 DEG C;After the heating
Slab be hot-rolled down to finish to gauge terminate temperature be 760 DEG C~850 DEG C and the step of obtain hot rolled steel plate;By hot rolled steel plate to be greater than
Or the step of being cooled to equal to the cooling velocity of 5 DEG C/s less than or equal to 450 DEG C;And the hot rolled steel plate after cooling is added
The normalizing heat treatment step of [1.3t+ (10~30)] minute is kept after the temperature range of heat to 850 DEG C~960 DEG C.The t is pair
The value that the thickness of hot rolled steel plate is determined as unit of mm.
Heating of plate blank step
By the heating of plate blank with above-mentioned alloy compositions to 1050 DEG C~1200 DEG C.
If heating temperature is greater than 1200 DEG C, austenite grain meeting coarsening, it is possible to toughness is reduced, if heating temperature
Degree is less than 1050 DEG C, then Ti, Nb etc. will not be sufficiently dissolved, and intensity may decline.
Hot-rolled step
Be hot-rolled down to finish to gauge to the slab after the heating and terminate temperature and is 760 DEG C~850 DEG C and obtains hot rolled steel plate.
The rolling temperature of general heat treatment steel is 850 DEG C~1000 DEG C or so, using pair rolling.But at this
In invention, it is important that initial tissu is formed as bainite.Therefore, it is necessary to the roll controls for terminating rolling at low temperature
Process, to substitute the pair rolling for Ferrite-Perlite structure occur.
It in hot rolling, needs to carry out recrystallization zone rolling, so that austenite grain size refines, and reduction ratio per pass
More increase more advantageous on aspect of performance.
Unhydrated cement rolling should terminate under the Ar3 temperatures above of steel, refer to about 760 DEG C or more.More specifically, can
760 DEG C~850 DEG C are defined as so that finish to gauge is terminated temperature.If finish to gauge terminates temperature greater than 850 DEG C, it is difficult to inhibit iron plain
Body-perlitic transformation, if finish to gauge terminates temperature less than 760 DEG C, it is likely that cause the unevenness of the microscopic structure of thickness direction
It is even, and because the drafts based on roll load weight is reduced, it is possible to the microscopic structure to be realized can not be formed.
By terminating finish to gauge under 760 DEG C~850 DEG C of temperature range, ferrite-pearlite can be inhibited to change, and lead to
Bainite structure is realized in supercooling.Initial tissu is by the purpose that bainite forms, and is uniformly distributed MA after heat treatment.Iron element
MA is mainly formed at crystal boundary in body-pearlitic structrure, and crystal boundary and intra-die are all formed with MA in bainite structure.
Cooling step
The hot rolled steel plate is cooled to the cooling velocity more than or equal to 5 DEG C/s less than or equal to 450 DEG C.
It is quickly cooled down after hot rolling extremely important to the destination organization of realization invention steel.In order to form fine, uniform MA, need
Bainite is formed, and in order to form bainite, cooling end temperature and cooling velocity are key factors.
If the cooling temperature that terminates is greater than 450 DEG C, the size of crystal grain may be become thick, coarse due to carbide
Change, will lead to form coarse MA after heat treatment, this is likely to cause toughness decline, and is difficult to ensure more than or equal to 50 faces
The bainite of product %.
If cooling velocity largely forms acicular ferrites or ferrite+pearlite microscopic structure less than 5 DEG C/s,
It may result in intensity decline, be not in the two-phase structure of ferrite+MA after heat treatment, but coarse ferrite+pearl occur
The quantity of body of light tissue or the second phase sharply declines, and there are problems that being difficult to ensure the bainite more than or equal to 50 area %.
Normalizing heat treatment step
The hot rolled steel plate after cooling is heated to keep after 850 DEG C~960 DEG C of temperature range [1.3t+ (10~
30)] minute.The t is the value determined as unit of mm to the thickness of hot rolled steel plate.
If normalizing temperature is less than 850 DEG C or the retention time is less than (1.3t+10) minute, in pearlite, bainite
Cementite and being dissolved again for MA phase can be difficult, therefore the C being dissolved is reduced, and is not only difficult to ensure intensity, but also is finally left
Hard phase can be coarse.
On the contrary, being present in shellfish if normalizing temperature is greater than 960 DEG C or the retention time is greater than (1.3t+30) minute
Carbide in family name's body crystal grain all migrate to crystal boundary or occur carbide coarsening, can not be formed final MA size and
Even distribution.Furthermore, it is also possible to which grain growth, which occurs, causes intensity decline and impact characteristics to be deteriorated.
Invention embodiment
Below by embodiment, the present invention will be described in more detail.But it is noted that following embodiments are only for description
The purpose of specific example of the invention, and be not intended to limit interest field of the invention.Interest field of the invention depends on power
The content of sharp claim and thus reasonable derived content.
Prepare the molten steel with component shown in the following table 1, then manufactures slab using continuous casting.To the slab according to following table
2 manufacturing condition rolled, is cooled down and normalizing heat treatment, to produce steel plate.
Bainite score and mechanical performance to normalizing heat treatment front spring are shown in the following table 3 after being measured.
Quantity and mechanical performance to the MA on the MA score of steel plate after normalizing heat treatment, average MA size, 100 μm of lines into
It is shown in the following table 4 after row measurement.It is exactly ferrite other than MA, ferritic average grain size is less than for example
Or it is equal to 20 μm, this is not recorded separately.
Average MA size is the average-size measured according to equivalent diameter.For the MA quantity on 100 μm of lines, in size
For in 100 μm of 100 μ m of microstructure pictures vertically or left and right draw 10 straight lines, to the quantity of the MA on each straight line
Par is described after being measured.
Specifically, it is intended to grasp to rolling temperature, the cooling influence for terminating temperature, heat treatment time.In addition, showing in table 3
MA score, yield tensile ratio and the mechanical performance of the steel plate according to ingredient A~H, the manufacture of manufacturing condition 1~12 are gone out.
[table 1]
Classification | Steel grade | C | Si | Mn | P | S | Al | Ni | Mo | Ti | Nb | Cu | N |
Invention steel | A | 0.045 | 0.086 | 1.87 | 0.005 | 0.002 | 0.006 | 1.19 | 0.13 | 0.007 | 0.008 | 0.242 | 0.0037 |
Invention steel | B | 0.04 | 0.095 | 1.92 | 0.004 | 0.0017 | 0.012 | 1.21 | 0.15 | 0.01 | 0.01 | 0.235 | 0.004 |
Invention steel | C | 0.043 | 0.105 | 1.88 | 0.005 | 0.0018 | 0.01 | 1.18 | 0.15 | 0.009 | 0.011 | 0.248 | 0.0038 |
Invention steel | D | 0.046 | 0.095 | 1.91 | 0.005 | 0.0018 | 0.011 | 1.21 | 0.16 | 0.008 | 0.01 | 0.251 | 0.0035 |
Compared steel | E | 0.12 | 0.12 | 1.87 | 0.005 | 0.0018 | 0.011 | 1.21 | 0.14 | 0.011 | 0.01 | 0.241 | 0.0035 |
Compared steel | F | 0.037 | 0.11 | 1.91 | 0.005 | 0.0017 | 0.013 | 1.21 | 0.012 | 0.012 | 0.012 | 0.253 | 0.0037 |
Compared steel | G | 0.04 | 0.11 | 0.85 | 0.0048 | 0.0017 | 0.012 | 1.17 | 0.13 | 0.01 | 0.012 | 0.255 | 0.0035 |
Compared steel | H | 0.042 | 0.13 | 1.88 | 0.0047 | 0.0018 | 0.01 | 0.23 | 0.12 | 0.01 | 0.011 | 0.239 | 0.0037 |
The unit of each constituent content is weight % in upper table 1.Invention steel A~D is to meet ingredient specified in the present invention
The steel plate of range, compared steel E~H are the steel plates for not meeting composition range specified in the present invention.Compared steel E is that C content is super
Steel out, compared steel F are the insufficient steel of Mo content, and compared steel G is the insufficient steel of Mn content, and compared steel H is that Ni content is insufficient
Steel.
[table 2]
[table 3]
[table 4]
The example that the alloy compositions and manufacturing condition proposed in the present invention are all met may insure that yield tensile ratio is less than
Or it is equal to 0.65, the impact flexibility at -40 DEG C is also excellent to be greater than or equal to 100J.
For comparative example, that is, test number 6,7,9 and 10, although meeting the alloy compositions proposed in the present invention,
Do not meet manufacturing condition, therefore be unable to ensure sufficient low yield strength ratio, the impact flexibility at -40 DEG C is also poor to be less than 100J.
For comparative example, that is, test number 11 to 14, although meeting the manufacturing condition proposed in the present invention, do not have
Have and meet alloy compositions, therefore is unable to ensure sufficient low yield strength ratio, the impact flexibility at -40 DEG C of test number 11 and 14
Difference is less than 100J.
From upper table 4 it is found that example MA score compared with comparative example is high.From upper table 3 it has been confirmed that this is indicated by just
Ensure higher bainite score before burning hot processing, in the crystal grain of initial bainite structure, the Carbides Transformation on crystal boundary at
Fine MA.
From shooting example, that is, test number 1 microscopic structure Fig. 1 and Fig. 2 it is found that being formed in microscopic structure fine
And uniform MA.
In contrast, from Fig. 3 of the microscopic structure of shooting comparative example, that is, test number 12 it is found that carbide, pearlite are made
Occur for main two-phase, therefore the score of MA is low, and being formed by MA is polygonal shape, is primarily present in grain boundaries.
The technology of the invention for describing the present invention above with reference to embodiment, but being recorded in without departing from claims
In the range of thought and field, those of ordinary skill in the art can be with various modification can be adapted and change.
Claims (9)
1. a kind of high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness, it is characterised in that:
The steel plate includes 0.03%~0.08% C, 0.05%~0.3% Si, 1.0%~2.0% in terms of weight %
Mn, 0.005%~0.04% Al, 0.005%~0.04% Nb, 0.001%~0.02% Ti, 0.05%~0.4%
Cu, 0.6%~2.0% Ni, 0.08%~0.3% Mo, 0.002%~0.006% N, be less than or equal to 0.01%
P, less than or equal to 0.003% S, the Fe and inevitable impurity of surplus,
Comprising 80%~92% ferrite, 8%~20% MA, (martensite/austenite is mixed in terms of area fraction for microscopic structure
It is combined and knits), the average-size according to equivalent diameter measurement of the MA is less than or equal to 3 μm.
2. the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness according to claim 1, it is characterised in that:
When drawing 100 μm of straight lines on the steel plate, there are 5~13 MA on the straight line.
3. the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness according to claim 1, it is characterised in that:
The ratio of the MA being present in inside the ferrite crystal grain and MA for being present in crystal boundary is 1:3~1:10.
4. the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness according to claim 1, it is characterised in that:
The ferritic average-size according to equivalent diameter measurement is less than or equal to 20 μm.
5. the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness according to claim 1, it is characterised in that:
The steel plate is the steel plate being heat-treated by normalizing,
The bainite of the microscopic structure of the normalizing heat treatment front spring is 50 area of area %~90 %.
6. the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness according to claim 1, it is characterised in that:
The yield tensile ratio of the steel plate is 0.5~0.65, and the low-temperature impact property at -40 DEG C is greater than or equal to 100J.
7. the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness according to claim 1, it is characterised in that:
The yield strength of the steel plate is 350MPa~400MPa, and tensile strength is greater than or equal to 600MPa.
8. a kind of manufacturing method of the high-strength steel sheet of low yield strength ratio characteristic and excellent in low temperature toughness, it includes:
The step of by heating of plate blank to 1050 DEG C~1200 DEG C, the slab in terms of weight % comprising 0.03%~0.08% C,
0.05%~0.3% Si, 1.0%~2.0% Mn, 0.005%~0.04% Al, 0.005%~0.04% Nb,
0.001%~0.02% Ti, 0.05%~0.4% Cu, 0.6%~2.0% Ni, 0.08%~0.3% Mo,
0.002%~0.006% N, the P less than or equal to 0.01%, the S less than or equal to 0.003%, surplus Fe and can not keep away
The impurity exempted from;
Be hot-rolled down to finish to gauge to the slab after the heating and terminate temperature and is 760 DEG C~850 DEG C and obtains the step of hot rolled steel plate
Suddenly;
The step of hot rolled steel plate is cooled to the cooling velocity more than or equal to 5 DEG C/s less than or equal to 450 DEG C;And
[1.3t+ (10~30)] point are kept after the hot rolled steel plate after cooling to be heated to 850 DEG C~960 DEG C of temperature range
The normalizing heat treatment step of clock,
Wherein, the t is the value determined as unit of mm to the thickness of hot rolled steel plate.
9. the manufacturing method of the high-strength steel sheet of low yield strength ratio characteristic according to claim 8 and excellent in low temperature toughness,
It is characterized in that:
The bainite of the microscopic structure of the hot rolled steel plate after cooling is 50 area of area %~90 %.
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PCT/KR2017/006956 WO2018004297A1 (en) | 2016-07-01 | 2017-06-30 | High strength steel plate having excellent low yield ratio characteristics and low temperature toughness and method for manufacturing same |
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JP2019524987A (en) | 2019-09-05 |
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WO2018004297A1 (en) | 2018-01-04 |
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