CN101558178A - Cold-rolled steel sheet with high yield ratio and excellent weather resistance - Google Patents

Cold-rolled steel sheet with high yield ratio and excellent weather resistance Download PDF

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Publication number
CN101558178A
CN101558178A CNA2007800455344A CN200780045534A CN101558178A CN 101558178 A CN101558178 A CN 101558178A CN A2007800455344 A CNA2007800455344 A CN A2007800455344A CN 200780045534 A CN200780045534 A CN 200780045534A CN 101558178 A CN101558178 A CN 101558178A
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steel
cold
steel sheet
rolled steel
yield
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CN101558178B (en
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金在翼
郑琪朝
金钟华
李秀姬
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Posco Holdings Inc
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Posco Co Ltd
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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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron

Abstract

There is provided a cold-rolled steel sheet with a high yield ratio, and excellent weather resistance and workability. The cold-rolled steel sheet including, by weight: 0.08 to 0.20% C, 0.1 to 0.5% Si, 0.9 to 2.0% Mn, <0.02% P, <0.01% S, 0.02 to 0.07% Al, 0.03 to 0.06% Nb, 0.05 to 0.30% Ni, 0.2 to 0.5% Cu, 0.3 to 0.6% Cr, 0.001 to 0.004% B, 0.02 to 0.08% Co, the balance being Fe and unavoidable impurities. Also, there is provided a method of manufacturing the same.

Description

Cold-rolled steel sheet with high-yield-ratio and excellent weather resistance
Technical field
The present invention relates to a kind ofly to be used to build, the high strength cold rolled steel plate and the manufacture method thereof with excellent weather resistance (weather resistance) of track vehicle and freight container, more specifically, the present invention relates to a kind of high strength cold rolled steel plate with high-yield-ratio and excellent weather resistance.
Background technology
For the weight that alleviates freight container or track vehicle or prolong its work-ing life, generally use as stainless steel or aluminium class material.These products have all required for example characteristics such as bendability, weldability and weather resistance.In addition, therefore transportation means needs to suppress the distortion that surging force causes transporting or be vulnerable to during lade surging force.For this purpose, can desirably use steel with high-yield-ratio.
Yield tensile ratio is defined as the ratio of tensile strength and yield strength, the numerical value (steel value) of the steel that obtain for Elongation test.Under the identical tensile strength, the high more steel yield strength of just representing of yield tensile ratio is big more.That is, high-yield-ratio steel its distortion resistibility when being applied in surging force is bigger, and this is because high-yield strength is the characteristic of resilient material, thereby further energy resistance to deformation.The yield tensile ratio of the steel that use in the freight container may be at least 80%.Especially, freight container should be able to stand various land or the oceanic climate condition with the transportation environment variation.This just needs steel to have excellent weather resistance.
For example, the SPA-C of common for example Korea S's standard K S-D3542 and Nippon Standard JIS-G3125 regards the rolling stock with excellent weather resistance as.Yet the tensile strength of this steel is lower, is 50kg/mm 2, therefore when being used to make relatively large product, can gain in weight.This can improve transportation cost.And tensile strength is 60-80kg/mm 2High strength cold rolled steel plate be applied in the structure unit of automobile.Yet what people paid close attention at present is the intensity that increases these class steel, does not therefore show required good weathering resistance.
Recently, in the freight container industry, attempted making van container to guarantee lower cost and to solve environmental problem, improved conveying efficiency thus by reducing its size significantly.Especially, need a kind of have excellent weather resistance and 80kg/mm at least 2High-intensity steel, and its manufacture method has been proposed.
For example, the open flat 7-207408 of text of Japanese Patent discloses a kind of method of making hot-rolled steel sheet.In the method, will contain≤0.008% C, 0.5% to 2.5% Si, 0.1% to 3.5%Mn, 0.03% to 0.20% P ,≤0.01% S, 0.05% to 2.0% Cu, 0.005% to 0.1%Al ,≤0.008% N, 0.05% to 6.0% Cr, 0.05% to 2.0% Ni, 0.05% to 3.0%Mo and the steel of 0.0003% to 0.002% B be heated to 1100-1300 ℃.Then, at 800-950 ℃ of these steel of finish rolling, and batch at 400-700 ℃.But this technology has only limited example to produce and has 60-70kg/mm 2The steel plate of tensile strength, most of examples produce be that tensile strength is 50kg/mm 2Steel plate, can't reach 80kg/mm thus 2Tensile strength.In addition, add a large amount of hardenability enhancing ingredients such as Cr and Mo, this can reduce weldability and increase production cost.
In addition, the open flat 11-21622 of text of Japanese Patent discloses a kind of method of making steel product.In the method, will consist of by weight :≤0.15%C ,≤0.7% Si, 0.2% to 1.5% Mn, 0.03% to 0.15% P ,≤0.02% S ,≤0.4% Cu, 0.01% to 0.1% Al ,≤steel of 0.1% Cr, 0.4% to 4.0% Ni and 0.1% to 1.5% Mo are heated to 1050-1300 ℃.Then, at 950 ℃ or exceed these steel of temperature hot rolling of at least 40%, 900-750 ℃ of finish rolling, the sector-style of going forward side by side is cold.Yet even use this technology, the tensile strength of most steel product is 50kg/mm 2, only limited steel product shows 60kg/mm 2Tensile strength.It is 50kg/mm that this technology generally is used to make tensile strength 2Steel plate.
In addition, a large amount of P of adding 0.03% to 0.15% is to improve the erosion resistance under the briny environment.But the P of heavy addition can cause cold-rolled steel section product center segregation, thereby destroys its workability rapidly.
In addition, the open flat 6-104858 of text of Japanese Patent discloses a kind of method of making steel plate.In the method, will contain 0.02% to 0.12% C ,≤0.5% Si, 0.1% to 2.0%Mn, 0.07% to 0.15% P ,≤0.02% S, 0.25% to 0.55% Cu, 0.01% to 0.05% Al, 0.3% to 1.25% Cr ,≤0.006% N 2, 0.06% to 0.20% Ti the composition of steel transfer to and satisfy formula 12.1X Ti.eff(%)/Mn (%)＞1.0.These steel are reheated to 1180 ℃ or higher temperature, 880-950 ℃ of hot rolling, and 650 ℃ or more low temperature batch.By this technology, add Ti relatively with the control precipitation with Mn content.But the tensile strength of the steel plate of each examples produce of this technology is 60kg/mm 2, be lower than 80kg/mm 2, and target of the present invention is to reach 80kg/mm 2Tensile strength.
Summary of the invention
Technical problem
The present invention has solved aforesaid the problems of the prior art, so an aspect of of the present present invention provides a kind of steel plate with high-yield-ratio and excellent weather resistance, particularly, provides a kind of 80kg/mm of being at least that has 2High-tensile steel plate.
Technical scheme
According to an aspect of the present invention, the invention provides a kind of have high-yield-ratio and excellent weather resistance cold-rolled steel sheet, it comprises, by weight: 0.08% to 0.20% C, 0.1% to 0.5%Si, 0.9% to 2.0% Mn ,≤0.02% P ,≤0.01% S, 0.02% to 0.07% Al, 0.03% to 0.06% Nb, 0.05% to 0.30% Ni, 0.2% to 0.5% Cu, 0.3% to 0.6% Cr, 0.001% to 0.004% B, 0.02% to 0.08% Co, all the other are Fe and unavoidable impurities.
The tensile strength of described cold-rolled steel sheet can be 80kg/mm at least 2
According to a further aspect in the invention, the invention provides a kind of method of making the high-yield-ratio cold-rolled steel sheet, described method comprises: steel are reheated to 1150 to 1300 ℃, described steel comprise, by weight: 0.08% to 0.20% C, 0.1% to 0.5% Si, 0.9% to 2.0%Mn, ≤ 0.02% P, ≤ 0.01% S, 0.02% to 0.07% Al, 0.03% to 0.06% Nb, 0.05% to 0.30% Ni, 0.2% to 0.5% Cu, 0.3% to 0.6% Cr, 0.001% to 0.004% B, 0.02% to 0.08% Co, all the other are Fe and unavoidable impurities; These steel of final rolling temperature hot rolling at 850-950 ℃; Rate of cooling with per second 20-40 ℃ is cooled off this steel; Batch this steel at 500-650 ℃; The cold rolling steel that this batches; And at 500 ℃ to A 1Make this steel continuous annealing in the temperature range of transition point.
Beneficial effect
According to the present invention, steel plate can obtain weathering resistance, mechanical property and high-yield-ratio.Therefore, this steel plate with high added value of gained thus can use under needs are resisted the situation of surging force.In addition, in relatively low temperature range, carry out continuous annealing, thereby save the energy and improved annealing efficiency.
Embodiment
Now describe exemplary of the present invention in detail.
But the present inventor a kind ofly has multiple processing characteristics and weathering resistance and guarantees high strength and thereby the steel plate of high-yield-ratio has carried out research and experiment repeatedly and finished the present invention for obtaining.According to the present invention, in the weather-proof composition system of Cu-Co, the add-on of Cr, B and Nb is regulated, to obtain high-strength characteristic and high-yield-ratio.
Preferably, the scope of carbon (C) is 0.08 weight % to 0.20 weight % (hereinafter only being called per-cent %).
Add C for increasing armor plate strength.The amount that strengthens C can increase the tensile strength and the yield tensile ratio of steel plate.But when adding excessive C, the workability of steel can descend.The C that therefore, can add the amount of as many as 0.20%.Simultaneously, the C amount will be not enough to promote precipitation less than 0.08%.
Preferably, the scope of silicon (Si) is 0.1% to 0.5%.
Si is used for deoxidation of molten steel effectively and is strengthened sosoloid.Si and Fe at high temperature form fine and close Fe on the steel surface layer 2SiO 4Oxide compound plays the effect that improves erosion resistance.Be fully to obtain these effects, can add the Si of at least 0.1% amount.Therefore, should add Si and improve weathering resistance, but excessive Si can reduce weldability and coating property.The Si that therefore, can add the amount of as many as 0.5%.
Preferably, the scope of manganese (Mn) is 0.9% to 2.0%.
Mn is used to strengthen sosoloid effectively, and very important aspect increase steel strength and hot rolling workability.Yet owing to can form MnS, Mn also can hinder the ductility and the workability of steel.A spot of Mn is favourable for workability, but also can cause the steel strength deficiency.Therefore, can add the Mn of at least 0.9% amount to reach required intensity.On the other hand, Mn is a kind of alloying element of costliness, and excessive Mn can reduce economical efficiency, and the infringement weldability.The Mn that therefore, can add the amount of as many as 2.0%.
Preferably, the scope of phosphorus (P) is at least 0.02%.
P can strengthen the erosion resistance of steel, therefore can add a large amount of P to increase erosion resistance.Yet P can cause the serious center segregation in the steel castingprocesses.Therefore, a large amount of P can reduce weldability and tensile strength.The P that therefore, can add the amount of as many as 0.02%.
Preferably, the scope of sulphur (S) is as many as 0.01%.
Known S is effective to increase erosion resistance, but when when Mn in the steel combines, they can form can cause the corrosive non-metallic inclusion.Therefore, can add S as far as possible on a small quantity.Thus, the as many as 0.01% of the add-on of S, especially, as many as 0.005%.
Preferably, the scope of aluminium (Al) is 0.02% to 0.07%.
Al is effective to deoxidation of molten steel usually and increases erosion resistance, but excessive Al can increase the amount of inclusion in the steel, thereby destroys workability.Therefore, the amount of Al can be set in 0.02% to 0.07% scope.
Preferably, the scope of niobium (Nb) is 0.03% to 0.06%.
Nb can postpone ferritic recrystallization, and can with C and the N in the steel 2In conjunction with and precipitated, strengthen the intensity of steel plate thus.Be to obtain desirable strength, can add 0.03% or more Nb.Simultaneously, the amount of Nb surpasses at 0.06% o'clock can increase production cost, and hinders the hot rolling processibility.
Preferably, the scope of nickel (Ni) is 0.05% to 0.3%.
Ni generally can stop the steel that add Cu to rupture in castingprocesses, and can strengthen erosion resistance.The Ni that can add at least 0.05% amount is to realize above-mentioned effect.Yet, when surpassing 0.3%, the amount of Ni can weaken erosion resistance, and owing to too much using this expensive alloying element to increase cost.
Preferably, the scope of copper (Cu) is 0.2% to 0.5%.
Cu can form stable rusty scale under aggressive atmosphere, thereby strengthens erosion resistance.For obtaining required erosion resistance, can add 0.2% or more Cu.Yet the amount of Cu surpasses 0.5% o'clock crystal boundary cracking that can cause in the continuous casting process, and can make the hot-rolled steel sheet surface become coarse.
Preferably, the scope of chromium (Cr) is 0.3% to 0.6%.
Cr is similar to Cu, can be used for forming stable rusty scale.Be to obtain erosion resistance and intensity, can add 0.3% or more Cr.Simultaneously, when the amount of Cr surpasses 0.6%, can cause crevice corrosion, and significantly increase production cost.
Preferably, the scope of boron (B) is 0.001% to 0.004%.
B can strengthen the hardenability of steel, also can postpone the recrystallization of ferritic phase.For obtaining desirable strength at low temperatures, can add the B of at least 0.001% amount.Simultaneously, the amount of B surpasses at 0.004% o'clock, because hardenability increases, thereby can promote hard for example bainite growth mutually in the course of hot rolling, thereby hinder cold rolling processibility.
Preferably, the scope of cobalt (Co) is 0.02% to 0.08%.
Co can react and the erosion resistance of acquisition steel with Cu that adds and Cr, can suppress upper layer corrosive product thereby promote to form.For realizing this effect, can add 0.02% or more Co.Yet the amount of Co surpasses at 0.08% o'clock and can cause the production cost increase and can not bring better erosion resistance.
Steel of the present invention contain said components, and all the other components are Fe and unavoidable impurities.Choose wantonly and can add alloying element has the steel of good weatherability properties with improvement characteristic.At this, even if in the composition of this cold-rolled steel sheet, added the alloying element of not addressing in the example embodiment of the present invention, the scope of the present invention that also should not be construed as this alloy elements.
Cold-rolled steel sheet of the present invention has high strength and high-yield-ratio simultaneously.According to an example embodiment of the present invention, the tensile strength of this steel plate is 80kg/mm at least 2, 80-110kg/mm for example 2The yield strength of this steel plate is at least 80%, for example 85% to 94%.In addition, this steel plate has at least 10% ductility.
These characteristics satisfy the needs of mentioned component system, and can obtain by low-temperature annealing of the present invention.Described low-temperature annealing can make deformed grains partly be retained in the microstructure, but not recovers fully.Microstructure of the present invention can be ferrite or ferrite and pearlitic mixture, but is not limited to these.
The method of making cold-rolled steel sheet hereinafter will be described.
Example embodiment explaination according to the present invention had the manufacture method of the steel of above-mentioned composition.The steel that will have above-mentioned chemical constitution reheat to 1150-1300 ℃, and 850-950 ℃ of hot finishing.Then, cool off this steel with per second 20-40 ℃ rate of cooling, and batch at 500-650 ℃.Subsequently, carry out cold rolling and thermal treatment, make steel continuous annealing in the temperature range of 500 to A1 transition points.This manufacture method produces the cold-rolled steel sheet with high-yield-ratio and excellent weather resistance, and particularly, this steel plate has 80kg/mm at least 2Strong tensile strength.
When these steel are reheated when being lower than 1150 ℃ the insufficient center segregation that is easy to generate of curing crystalline-granular texture destruction that forms in can be owing to castingprocesses.Therefore, the final crystal grain that forms mixes and significantly reduces the workability and the impelling strength of steel.And reheated when being higher than 1300 ℃ fouling due to can the promotes oxidn effect when these steel, thereby cause flaggy thickness significantly to reduce.In addition, in this case, reduce the impelling strength of steel owing to coarse grain.
In addition, this higher temperature that reheats can cause economically loss.Therefore, steel reheats the scope that temperature can be set in 1150-1300 ℃.
When the hot finishing temperature is higher than 950 ℃, can't make steel evenly hot rolling on whole thickness.Therefore, owing to causing the impelling strength of steel, reduces coarse grain.On the contrary, when the hot finishing temperature was lower than 850 ℃, steel are hot rolling at a lower temperature, thereby formed its crystal grain mixture.This can damage erosion resistance and workability, and therefore, the hot finishing temperature can be set in 850-950 ℃ scope.
After carrying out above-mentioned hot rolling, speed cooling steel that can 20-40 ℃.That is, when (run-out-table ROT) goes up with less than the rate of cooling cooling steel of 20 ℃ of per seconds the time, because grain growing is accelerated, forms thicker crystal grain relatively in the steel, makes intensity reduce thus at runoff table after hot finishing.Therefore, the rate of cooling of steel can be set in 20 ℃ of per seconds or low rate more.And rate of cooling can cause forming hard second for 40 ℃ mutually as bainite above per second, thereby significantly destroys cold rolling performance.Therefore, the cooling temperature of steel can be set in per second 20-40 ℃ scope.
After the cooling of above-mentioned steel, batch.Steel can batch at 500-650 ℃.The hot rolling reeling temperature can't produce enough sedimentation effects when surpassing 650 ℃, thereby reduce the intensity of steel.This just makes steel can not obtain required intensity 80kg/mm 2And be lower than at coiling temperature under 500 ℃ the situation, steel form hard mutually and kept when cooling, increased the rolling load of milling train in the cold-rolled process thus.This can hinder Steel Rolling, so the coiling temperature of steel can be set in 500-650 ℃ scope.
The hot rolled steel are rolled under common cold rolling condition, carry out continuous annealing then.At this moment, for obtaining required steel characteristics, steel need to anneal under suitable temperature.When annealing temperature was lower than 500 ℃ in the continuous annealing process, the crystal grain of distortion still existed when cold rolling, reduced ductility greatly and therefore damaged workability.
Simultaneously, annealing temperature is A 1Can form martensitic phase owing to steel take place to change when transition temperature or higher temperature when annealing postcooling.This can make the yield strength of steel reduce to 60% or lower, makes steel easily deformable.Therefore, can make steel be up to A 1The annealing temperature of transition point.
According to the present invention, cold annealing temperature can make the crystal grain that is out of shape in the cold-rolled process partly be retained in the cold-rolled steel sheet.
Embodiment of the present invention
Hereinafter will the present invention be described in more detail by the mode of embodiment.
Embodiment 1
Measurement has the standardized corrosion resistance index (CI) and the weathering resistance of the steel of forming shown in the table 1.The results are shown in the table 2.
In atmospheric exposure test, steel were carried out salt-fog test (SST) 480 hours at 30 ℃, salt solution (NaCl solution) with 5%.Herein, corrosion resistance index (CI) is to estimate the index of weathering resistance according to ASTMG101.The high more expression weathering resistance of corrosion resistance index is strong more.
Corrosion resistance index mainly obtains based on alloying element, and satisfies following formula.
Corrosion resistance index (CI)≤26.01 (%Cu)+3.88 (%Ni)+1.2 (%Cr)+1.49 (%Si)+17.28 (%P)-7.29 (%Cu) is (%Ni) (%P)-33.39 (%Cu) (%Ni)-9.10 2
Table 1
Figure A20078004553400101
Table 2
Steel type Corrosion resistance index (CI) Erosion levels (weightlessness, g/cm 2) Weathering resistance is estimated
Steel 1 of the present invention 6.544475 0.0288 Excellent
Steel 2 of the present invention 6.748976 0.0278 Excellent
Comparative steel 1 6.779319 0.0295 Excellent
Comparative steel 2 3.454711 0.0601 Difference
Comparative steel 3 6.317656 0.0491 Difference
Comparative steel 4 6.419325 0.0338 Difference
As shown in table 2, the corrosion resistance index of comparative steel 2 is low, and corrodibility is weightless high, therefore is difficult to as weather-proof steel.Comparative steel 3 and comparative steel 4 corrosion resistance index are high slightly, but its corrodibility weightlessness in salt-fog test is 0.030g/cm 2Perhaps higher.
Therefore, comparative steel 3 and comparative steel 4 demonstrate relatively poor weathering resistance.Simultaneously, consider weightlessness and corrosion resistance index that corrosion causes, steel 1 of the present invention and 2 and comparative steel 1 demonstrate excellent weathering resistance.
Embodiment 2
---being the steel of the present invention 1 and 2 and comparative steel 1-4 in the table 1 of embodiment 1---with each steel is used for making cold-rolled steel sheet under the described condition of table 3.But measure the mechanical characteristics and the processing characteristics of each steel plate, the results are shown in the table 4.
Table 3
Figure A20078004553400121
Table 4
Classification Yield strength (kgf/mm 2) Tensile strength (kgf/mm 2) Unit elongation (%) Yield tensile ratio (%) Bendability
The embodiment of the invention 1 84.9 90.4 11 93.9 Excellent
The embodiment of the invention 2 82.1 92.4 13 88.9 Excellent
The embodiment of the invention 3 86.3 101.0 10 85.4 Excellent
The embodiment of the invention 4 83.8 95.2 12 88.0 Excellent
Comparative Examples 1 96.4 106.1 3 90.9 Cracking
Comparative Examples 2 46.5 82.1 19 56.6 Excellent
Comparative Examples 3 92.2 104.1 2 88.6 Cracking
Comparative Examples 4 98.2 99.1 1 99.1 Cracking
Comparative Examples 5 56.3 82.9 8 67.9 Cracking
Comparative Examples 6 55.9 86.8 17 64.4 Excellent
Comparative Examples 7 101.0 104.7 4 96.5 Cracking
Comparative Examples 8 79.2 81.0 2 97.8 Cracking
Comparative Examples 9 79.8 82.2 2 97.1 Cracking
Comparative Examples 10 84.6 85.3 2 99.2 Cracking
Comparative Examples 11 46.5 72.5 24 64.1 Excellent
As shown in table 4, the embodiment of the invention 1-4 that chemical constitution and working condition satisfy condition of the present invention obtains to be respectively 80kgf/mm at least 2Tensile strength, at least 80% yield tensile ratio and at least 10% ductility.Embodiments of the invention do not ftracture in BENDING PROCESS, therefore can be made into the steel plate of high strength and high-yield-ratio.
Simultaneously, chemical constitution satisfies the condition of steel of the present invention but the Comparative Examples 1-5 of working condition outside the scope of the invention do not obtain required characteristic.That is, though annealing temperature is higher than Comparative Examples 2 of the present invention and Comparative Examples 5 has obtained its yield tensile ratio of required tensile strength and reduce to 70% or lower.This is because because the annealing temperature height, the transformation in the process of cooling forms second phase, and yield strength is reduced.That is to say that Comparative Examples 2 and Comparative Examples 5 do not obtain at least 80% yield tensile ratio, weakened resistibility thus distortion.
Be lower than in the Comparative Examples 4 of the present invention in annealing temperature, the cold rolling middle most deformed grains that form still exist, and therefore can not guarantee ductility and bendability.In addition, hot finishing temperature and coiling temperature Comparative Examples 1 and the rate of cooling Comparative Examples 3 that is higher than condition of the present invention outside scope of the present invention demonstrates ductility less than 5%, therefore do not obtain suitable workability.
When Mn and Cr compositing range outside the requirement of the present invention but the relative more excellent comparative steel 1 of weathering resistance when under condition of the present invention, making (Comparative Examples 7), Comparative Examples 1 does not obtain ductility and workability.In addition, when the rising annealing temperature when guaranteeing ductility and workability owing to form two-phase, the yield strength of Comparative Examples 1 reduces, and therefore obtains at least 80% yield tensile ratio.
When the comparative steel 2 to 3 (Comparative Examples 8-11) under different working conditions that chemical composition range departs from requirement of the present invention and do not obtain weathering resistance be can not determine the workability of each steel and suitable compositing range when testing.

Claims (3)

1. cold-rolled steel sheet with high-yield-ratio and excellent weather resistance, described cold-rolled steel sheet comprises, by weight:
0.08% to 0.20%C, 0.1% to 0.5%Si, 0.9% to 2.0%Mn ,≤0.02%P ,≤0.01%S, 0.02 to 0.07%Al, 0.03% to 0.06%Nb, 0.05% to 0.30%Ni, 0.2% to 0.5%Cu, 0.3% to 0.6%Cr, 0.001% to 0.004%B, 0.02% is to 0.08%Co, and all the other are Fe and unavoidable impurities.
2. the cold-rolled steel sheet of claim 1, the tensile strength of wherein said cold-rolled steel sheet is at least 80kg/mm 2
3. method of making the high-yield-ratio cold-rolled steel sheet, described method comprises:
Steel are reheated to 1150 to 1300 ℃, described steel comprise, 0.08% to 0.20%C, 0.1% to 0.5%Si, 0.9% to 2.0%Mn by weight: ,≤0.02%P ,≤0.01%S, 0.02% to 0.07%Al, 0.03% to 0.06%Nb, 0.05% to 0.30%Ni, 0.2% to 0.5%Cu, 0.3% to 0.6%Cr, 0.001% to 0.004%B, 0.02% is to 0.08%Co, and all the other are Fe and unavoidable impurities;
The described steel of final rolling temperature hot rolling at 850 to 950 ℃;
Rate of cooling with 20 to 40 ℃ of per seconds is cooled off described steel;
Batch described steel at 500 to 650 ℃;
The cold rolling described steel that batch; With
At 500 ℃ to A 1Make described steel continuous annealing in the temperature range of transition point.
CN2007800455344A 2006-12-12 2007-12-10 Cold-rolled steel sheet with high yield ratio and excellent weather resistance and its manufacture method Expired - Fee Related CN101558178B (en)

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