CN1405352A - Cold-rolled steel plate and galvanized steel plate with exceuent forming property, surface shaping property and anti-rabbing and manufacture method thereof - Google Patents

Abstract

A cold rolled steel plate of excellent moldability, panel shape characteristics and denting resistance which has steel composition comprising 0.005-0.015 wt.% of C, 0.01-0.2 wt.% of Si, 0.2-1.5 wt.% of Mn, 0.01-0.07 wt.% of P, 0.006-0.015 wt.% of S, 0.01-0.08 wt.% of sol. Al, not less than 0.004 wt.% of N, not less than 0.003 wt.% of O, 0.04-0.23 wt.% of Nb, wherein 1.0 <= (Nbx12)/(Cx93) <= 3.0, and the remainder substantially comprising Fe and unavoidable impurities, and which satisfies the following expression: exp( epsilon ) x (5.29 x exp( epsilon ) - 4.19) <= sigma / sigma 0.2 <= exp( epsilon ) x (5.64 exp( epsilon ) - 4.49) wherein 0.002 < epsilon <= 0.096; epsilon is true strain; sigma 0.2 0.2 % of proof stress; and sigma true stress with respect to epsilon.

Description

Cold-rolled steel sheet and steel plate galvanized and manufacture method thereof with excellent formability, panel shape stability and anti-rabbing property

Related application

The application is to be on September 24th, 1998 applying date, and application number is 98806617.3, and what denomination of invention was identical divides an application.

Technical field

The present invention relates to a kind of cold-rolled steel sheet and steel plate galvanized and manufacture method thereof, this steel plate has excellent formability, panel shape stability and anti-rabbing property, satisfies the requirement of automobile external panel.

Background technology

The automobile external steel plate for panel requires to have excellent formability, panel shape stability and anti-rabbing property (opposing local dent).Panel forming is estimated by index such as yield strength, unit elongation and n value (work hardening exponent).Panel shape stability and anti-rabbing property are in many cases also with the yield strength evaluation after yield strength and processing and the coating-baking vanish processing.If the steel plate yield strength weakens, press formability improves so., the anti-rabbing property behind the panel forming can not be satisfactory.On the other hand, if the yield strength of steel plate increases, anti-rabbing property improves so., aspect press formability, have problems as gauffer or crackle occurring.At this situation, carried out that various researchs make great efforts to obtain to have low yield-point when press forming and be shaped and baking vanish after have high yield strength steel plate, with as the automobile external panel.As at the cold-rolled steel sheet that satisfies these two kinds of contradiction demands aspect the yield strength, developed a kind of bake hardening steel of using carbon atom strain aging phenomenon in the steel, hereinafter referred to as " BH steel plate ".

Particularly, a kind of manufacturing of having known has in the method for BH steel plate of outstanding deep drawability, prepare cold-rolled steel sheet by add the element that can form carboritride such as Nb and Ti in the steel with low carbon content very (approximately 50ppm), wherein the addition of these elements is not more than 1 with the atomic ratio of carbon.For example, Japanese Patent open (Kokoku) No.60-46166 points out the soft steel that adds Ti or Nb is annealed under near 900 ℃ high temperature, makes specific BH steel plate.Open (Kokai) No.61-276928 of Japanese Patent points out to make Ultra-low carbon BH steel plate by annealing in 700～850 ℃ temperature range.

In JP ' 166 disclosed technology, advantage is to improve BH performance and r value.Yet, owing to be at high temperature to anneal, the surface irregularity that probably exists ferrite crystal grain to grow up to cause.In addition, because steel plate itself is soft,, not high enough through the yield strength after press forming and the baking vanish step although can obtain high BH performance.On the other hand, in JP ' 928 disclosed technology, it is low that same JP ' 166 compares annealing temperature, therefore surface property and the yield strength that meets the demands., can not improve the BH performance and the r value of requirement basically.It should still be noted that these prior art main purposes are to improve the BH performance of steel plate, so that make steel plate have improved anti-rabbing property.Therefore, the deterioration of anti-natural ageing performance probably occurs, tensile deformation just occurs when pressure forming, this results from the elongation at yield point that steel plate takes place when room temperature storage.In this case, with regard to the actual use of steel plate, the BH amount is limited in about 60MPa.

As mentioned above, the cold-rolled steel sheet of traditional method manufacturing can not satisfy surface property, anti-natural ageing performance and anti-rabbing property requirement, and this is that to be used for the steel plate of automobile external panel desired.

An object of the present invention is to provide a kind of satisfy cold-rolled steel sheet and steel plate galvanized and manufacture method thereof the requirement of automobile external panel, that have satisfied surface property, anti-natural ageing performance and anti-rabbing property.

Summary of the invention

(1) the invention provides a kind of excellent formability that has, the cold-rolled steel sheet of panel shape stability and anti-rabbing property, this steel plate contains the C of weight percent 0.005～0.015%, the Si of weight percent 0.01～0.2%, the Mn of weight percent 0.2～1.5%, the P of weight percent 0.01～0.07%, the S of weight percent 0.006～0.015%, the solid solution attitude Al of weight percent 0.01～0.08%, weight percent is not more than 0.004% N, weight percent is not more than 0.003% O, the Nb of weight percent 0.04～0.23% and the Fe of equal amount and unavoidable impurities, wherein Nb and C satisfy formula 1) expression relation, cold-rolled steel sheet satisfies formula 2) expression relation:

1.0≤(Nb％×12)/(C％×93)≤3.0???????????????…1)

exp(ε)×(5.29×exp(ε)-4.19)≤σ/σ _0.2≤exp(ε)×(5.64×exp(ε)-4.49)

…2)

0.002＜ε≤0.096 wherein, ε represents true strain, σ _0.2Represent 0.2% proof stress, σ represents the true stress with respect to true strain ε.

(2) the invention provides the cold-rolled steel sheet that a kind of as above-mentioned clause (1) is described, have excellent formability, panel shape stability and anti-rabbing property, this steel plate also comprises the B of weight percent 0.0001～0.002%.

(3) the invention provides a kind of steel plate galvanized with excellent formability, panel shape stability and anti-rabbing property, this steel plate passes through in clause (1) or zinc-plated acquisition above (2) described cold-rolled steel sheet.

(4) the invention provides a kind of manufacturing as above-mentioned clause (1) or (2) described, have the method for the cold-rolled steel sheet of excellent formability, panel shape stability and anti-rabbing property, comprise the following steps:

Preparation molten steel and this steel of continuous casting;

Carry out hot rolling and handle, wherein at (Ar ₃-100) ℃ or higher temperature finish to gauge, and steel plate batches at 500～700 ℃;

Hot-rolled steel sheet is carried out cold-rolling treatment and anneal continuously.

(5) the invention provides a kind of method of making steel plate galvanized, this steel plate has the described excellent formability of clause (3), panel shape stability and anti-rabbing property, comprises the following steps:

Preparation molten steel and the above-mentioned steel of continuous casting;

Carry out hot rolling and handle, wherein at (Ar ₃-100) ℃ or higher temperature carry out finish to gauge, and batch this steel plate at 500～700 ℃;

Hot-rolled steel sheet is carried out cold-rolling treatment and zinc-plated processing continuously.

(6) the invention provides a kind of cold-rolled steel sheet with outstanding panel surface shape stability and anti-rabbing property, this steel plate contains the C of weight percent 0.004～0.015%, the Si of weight percent 0.01～0.2%, the Mn of weight percent 0.1～1.5%, the P of weight percent 0.01～0.07%, the S of weight percent 0.005～0.015%, the solid solution attitude Al of weight percent 0.01～0.08%, weight percent is not more than 0.005% N, be selected from least a element in the group that the Ti by the Nb of weight percent 0.02～0.12% and weight percent 0.03～0.1% forms in addition, and the Fe of equal amount and unavoidable impurities, C wherein, Nb, Ti, N and S satisfy formula 1) expression relation, cold-rolled steel sheet satisfies formula 2) expression relation:

-0.001≤C%-(12/93) Nb%-(12/48) Ti ^*≤ 0.001 ... 1) wherein, Ti ^*=Ti%-(48/14) N%-(48/32) S% works as Ti ^*Be not more than at 0 o'clock, think Ti ^*Be 0.

Exp (ε) * (5.29 * exp (ε)-4.19)≤σ/σ _0.2≤ exp (ε) * (5.64 * exp (ε)-4.49) ... 2) 0.002＜ε≤0.096 wherein, ε represents true strain, σ _0.2Represent 0.2% proof stress, σ represents the true stress with respect to true strain ε.

(7) the invention provides the cold-rolled steel sheet that a kind of as above-mentioned clause (6) is described, have outstanding panel surface shape stability and anti-rabbing property, this steel plate also comprises the B of weight percent 0.0001～0.002%.

(8) the invention provides a kind of steel plate galvanized with outstanding panel surface shape stability and anti-rabbing property, this steel plate passes through in clause (6) or zinc-plated acquisition above (7) described cold-rolled steel sheet.

(9) the invention provides a kind of manufacturing as above-mentioned clause (6) or (7) described, have the method for the cold-rolled steel sheet of outstanding panel surface shape stability and anti-rabbing property, comprise the following steps:

At first prepare molten liquid steel and continuous casting Cheng Gang; Carry out hot rolling then and handle, wherein finishing temperature is (Ar ₃-100) ℃ or higher; And batch steel plate at 500～700 ℃;

Hot-rolled steel sheet is carried out cold-rolling treatment and anneal continuously.

(10) the invention provides a kind of method of making steel plate galvanized, this steel plate has described outstanding panel surface shape stability of clause (8) and anti-rabbing property, comprises the following steps:

At first prepare molten steel and continuous casting Cheng Gang; Carry out hot rolling then, wherein finishing temperature is (Ar ₃-100) ℃ or higher; And batch steel plate at 500～700 ℃;

Hot rolled strip is carried out cold-rolling treatment and zinc-plated processing continuously.

The accompanying drawing summary

Figure 1A and Figure 1B represent the steel plate according to first embodiment of the invention respectively, between its unit elongation El and (Nb * 12)/(C * 93) and the relation between r value and (Nb * 12)/(C * 93), wherein, the C=0.0075wt%～0.0095wt% of this steel plate, steel plate thickness=0.8mm.

Fig. 2 represents to estimate according to first embodiment of the invention the method for anti-rabbing property and shape stability.

Fig. 3 is a graphic representation, and expression is according to first embodiment of the invention, and how P0.1 (the anti-dent load when panel produces 2%, 4% and 8% strain) and δ (springback capacity when panel produces 2% strain) are subjected to σ/σ _0.2, exp (ε) and composition of steel influence.

Fig. 4 is that a graphic representation 2 is represented according to first embodiment of the invention, and how P0.1 (the anti-dent load when panel produces 2%, 4% and 8% strain) and δ (springback capacity when panel produces 2% strain) are subjected to σ/σ _0.2, exp (ε) and composition of steel influence.

Fig. 5 is a graphic representation, and expression is according to first embodiment of the invention, and how P0.1 (the anti-dent load when panel produces 2%, 4% and 8% strain) and δ (springback capacity when panel produces 2% strain) are subjected to σ/σ _0.2, exp (ε) and composition of steel influence.

Fig. 6 is a graphic representation, and expression is according to first embodiment of the invention, and how finishing temperature and coiling temperature influence P0.1 (the anti-dent load when panel produces 2% strain), δ and Wca (arithmetical av of wave height).

Fig. 7 represents according to second embodiment of the invention how to estimate the experiment of anti-rabbing property and shape stability.

Fig. 8 is a graphic representation, and expression is according to second embodiment of the invention, and how P0.1 (the anti-dent load when panel produces 2%, 4% and 8% strain) and δ (springback capacity when panel produces 2% strain) are subjected to σ/σ _0.2, exp (ε) and composition of steel influence.

Fig. 9 is a graphic representation, and expression is according to second embodiment of the invention, and how P0.1 (the anti-dent load when panel produces 2%, 4% and 8% strain) and δ (springback capacity when panel produces 2% strain) are subjected to σ/σ _0.2, exp (ε) and composition of steel influence.

Figure 10 is a graphic representation, and expression is according to second embodiment of the invention, and how P0.1 (the anti-dent load when panel produces 2%, 4% and 8% strain) and δ (springback capacity when panel produces 2% strain) are subjected to σ/σ _0.2, exp (ε) and composition of steel influence.

Figure 11 is a graphic representation, and expression is according to second embodiment of the invention, and how finishing temperature and coiling temperature influence P0.1 (the anti-dent load when panel produces 2% strain), δ and Wca (arithmetical av of fluctuation height).

Figure 12 is a graphic representation, and expression is according to the period of storage of the example 3 of second embodiment of the invention and the relation between the Δ YPel (the YPel amount of recovery behind the surface of steel plate dress rolling when storing for 25 ℃).Wherein, aging temp is 25 ℃, zero expression No. 6 steel samples (the present invention), and △ represents No. 18 steel samples (Comparative Examples).

Implement optimal mode of the present invention

For obtaining to be used as the steel plate of automobile external panel and to have cold-rolled steel sheet and the steel plate galvanized and the manufacture method thereof of satisfied surface property, anti-natural ageing performance and anti-rabbing property, inventors of the present invention have carried out extensive studies.

Found that the anti-rabbing property that can improve panel by alloy designs, the wherein work hardening behavior in the low strain zone in the panel forming stage that focuses on of alloy designs improves the desired anti-rabbing property of automobile external panel and be different from the prior art by increasing the BH value.Also find to give steel plate good surface properties and good anti-natural ageing by positive inhibition BH value.These results make inventors of the present invention can develop the technology of stable preparation cold-rolled steel sheet and steel plate galvanized, and this steel plate has outstanding panel surface forming property and anti-rabbing property and has the high-tensile of 340MPa at least.

Some embodiments of the present invention are described now.(first embodiment)

Describe below according to the use of first embodiment of the invention and add the reason of element, the reason that constituent content is added in restriction, the reason of restriction tensile properties and the reason of restriction processing condition.In the explanation hereinafter, " % " expression " weight percent "

(1) content of interpolation element

C：0.005～0.015％

The carbide that forms with Nb influences the work hardening of hanging down the strain zone in the panel forming process, to improving anti-rabbing property contribution is arranged.If C content is lower than 0.005%, can not obtain specific effect.If C content surpasses 0.015%, improve the anti-rabbing property of panel certainly., the panel shape stability suffers damage.Therefore reaching a conclusion requires C content in 0.005 to 0.015% scope.

Si：0.01～0.2％

Silicon can be strengthened steel effectively.Yet,, can not obtain solid solution strengthening effect if Si content is lower than 0.01%.On the other hand, if Si content surpasses 0.2%, the surface of steel plate performance suffers damage so.In addition, can produce the surfacial spalling defective after zinc-plated.Therefore, Si content should be in 0.01 to 0.2% scope.

Mn：0.2～1.5％

Mn is used to precipitate sulfide and suppresses thermoplastic deterioration.Mn also can strengthen steel effectively.If Mn content is lower than 0.2%, steel plate can produce red brittleness, causes yield strength to reduce.In addition, can not obtain the high mechanical strength feature of steel plate of the present invention.And Mn relates to the processability that improves steel, is necessary to the form of controlling MnS in hot-rolled process.Should be noted that at hot-rolled process causes tiny MnS particle to form by heavily molten and redeposition process.These MnS particles can hinder the grain growth of steel plate., if the content of Mn is not less than 0.2%, can eliminate so because the above-mentioned harm that causing appears in the MnS particle.In order to control MnS particulate form effectively at hot-rolled process, need add content at least and be 0.45% Mn.Yet if Mn content surpasses 1.5%, steel plate can harden and the shape stability of panel can deterioration so.Therefore reaching a conclusion requires Mn content in 0.2 to 1.5% scope.

P：0.01～0.07％

Phosphorus is the solution strengthening steel most effectively., if P content is lower than 0.01%, P can not show enough reinforcing properties so.On the other hand, if P content surpasses 0.07%, the plasticity of steel plate suffers damage so.And the Alloying Treatment operation in continuous zinc coating technology, can produce defective coating.Therefore, reach a conclusion and require P content in 0.01 to 0.07% scope.

S：0.006～0.015％

If the addition of sulphur surpasses 0.015%, can cause the hot-short of steel so., if S content is lower than 0.006%, the oxide skin stripping performance suffers damage in the hot-rolled process so, and produces tangible surface imperfection.Therefore, reach a conclusion and require S content in 0.006 to 0.015% scope.

Solid solution attitude Al:0.01～0.08%

Aluminium is used for steel-deoxidizing is become nitride with fix N.If Al content is lower than 0.01%, so fully deoxidation and fixed nitrogen.On the other hand, if Al content greater than 0.08%, the surface property of steel plate can deterioration so.Therefore, Al content should be in 0.01 to 0.08% scope.

N≤0.004％

Nitrogen is fixed as the form of AlN.Yet,, can not obtain the plasticity that steel plate needs so if N content surpasses 0.004%.Nature, N content should not surpass 0.004%.

O≤0.003％

Oxygen form relate to oxide compound inclusion, thereby have a strong impact on the grain growth of steel.If O content surpasses 0.003%, can damage grain growth at annealing stage so, can not obtain satisfied plasticity and satisfied panel shape stability.Nature, O content is should exceed 0.003% not.For the oxygen level in the steel that suppresses predetermined component of the present invention 0.003% or lower, be necessary to use best creating conditions.For example, solid solution attitude Al should be controlled at suitable contents level, and oxygen should be controlled in the treatment process behind the second time refinery practice.

Nb：0.04～0.23％

Niobium and C are in conjunction with forming tiny carbide particle.These tiny carbide particles influence the work hardening behavior in the panel forming stage, thereby help improving the anti-rabbing property of panel., if Nb content is lower than 0.04%, can not obtain specific effect so.On the other hand, if Nb content surpasses 0.23%, although anti-pressing against property raising some, panel shape stability such as rebound characteristics and surperficial amount of deflection deterioration.Nature, Nb content should be in 0.04 to 0.23% scope.

(Nb×12)/(C×93)：1.0～3.0

For improving the plasticity of steel plate, definitely must control (Nb * 12)/(C * 93) in the present invention.If the value of (Nb * 12)/(C * 93) is lower than 1.0, fixation of C so fully causes obtaining the high r value and the high-ductility of target call of the present invention., if its value surpasses 3.0, the Nb content that forms sosoloid so is too high, causes inductile.In the case, can not obtain the plasticity of target call of the present invention.Therefore, reaching a conclusion the value of requirement (Nb * 12)/(C * 93) should be in 1.0 to 3.0 scope.Figure 1A and Figure 1B represent relations between unit elongation El and (Nb * 12)/(C * 93), between r value and (Nb * 12)/(C * 93).

For improving the anti-rabbing property that requires, except above-mentioned interpolation element, require to add the B of following content.

B：0.0001～0.002％

If add B, crystal boundary is strengthened so, and the result has improved the performance of anti-second time of work brittleness.Ferrite crystal grain has also reduced, thereby guarantees the absolute value of yield strength, and improves anti-rabbing property., if B content less than 0.0001%, can not obtain these effects.On the other hand, if B content surpasses 0.002%, yield-point increases so, and the panel shape stability suffers damage.Therefore, reach a conclusion and require B content in 0.0001～0.002% scope.

(2) tensile properties

exp(ε)×(5.29×exp(ε)-4.19)≤σ/σ _0.2≤exp(ε)×(5.64×exp(ε)-4.49)

0.002＜ε≤0.096 wherein, ε represents true strain, σ _0.2Represent 0.2% proof stress, σ represents the true stress with respect to true strain ε.

In the steel plate of the present invention that contains the described interpolation element of aforesaid clause (1), Fe and unavoidable impurities.The flow stress σ that tension test obtains is with respect to 0.2% proof stress σ _0.2Ratio be σ/σ _0.2Should be between exp (ε) * (5.29 * exp (ε)-4.19) and exp (ε) * (5.64 * exp (ε)-4.49).Wherein, tension test condition is that true strain ε is not more than 0.096 i.e. 0.002＜ε≤0.096 greater than 0.002.

If σ/σ _0.2Be lower than above-mentioned lower limit, the anti-dent load under panel generation 2%P0.1,4%P0.1 and 8%P0.1 condition is up to 160～190N, shown in Fig. 3～5.For measuring anti-dent load, steel formability is a simulated panel as shown in Figure 2, wherein steel plate is applied 2%, 4% or 8% strain also subsequently 170 ℃ of thermal treatments of carrying out 20 minutes.Then, measure the load that makes the remaining displacement of simulated panel generation 0.1mm., if σ/σ _0.2Be lower than above-mentioned lower limit, springback capacity δ (to having 2% strained panel measuring) up to 7～10%, has damaged the panel shape stability so.On the other hand, if σ/σ _0.2Be higher than the above-mentioned upper limit, springback capacity δ little to 2～5% to improve the panel shape stability.Yet anti-rabbing property is low to 140～175N.In other words, can not improve anti-rabbing property.Under this condition, ratio σ/σ _0.2Should be in the scope between exp (ε) * (5.29 * exp (ε)-4.19) and exp (ε) * (5.64 * exp (ε)-4.49).

A kind of, cold-rolled steel sheet and steel plate galvanized with outstanding panel surface performance and anti-rabbing property desired as automobile external panel steel plate can obtain by controlling described interpolation elementary composition of aforesaid clause (1) and the described tensile properties of aforesaid clause (2).

This steel plate with property can be according to following method manufacturing.

(3) steel plate manufacturing process

In a first step, smelt the steel of the described composition of aforesaid clause (1).Usually use the converter method to smelt this steel, also can use the electric furnace method to smelt.The molten steel continuous casting becomes slab.Slab after the casting or cooled slab heat immediately, carry out hot rolling.Hot rolling is carried out under the following conditions: finishing temperature is set at and is not less than (Ar ₃-100) ℃, and the coiler plate temperature is set in 500～700 ℃.If finishing temperature is lower than (Ar ₃-100) ℃, 2%P0.1 (being the anti-dent load of panel when applying 2% strain) is low to 140～150N, as shown in Figure 6 so.In other words, can not improve anti-rabbing property.If coiling temperature is lower than 500 ℃, 2%P0.1 height, i.e. 155-165N., the springback capacity δ with 2% strained panel causes panel shape stability variation up to 8～10%.On the other hand, if coiling temperature is higher than 700 ℃, (i.e. fluctuation is arithmetical av highly for the Wca value so, measurement length is 25mm, near the panel crestal line, select the mean value of the observed value of 10 points) big, in the scope of a value between 0.4 and 0.6 μ m, cause the panel shape stability poor.Therefore, the finishing temperature of reaching a conclusion should be not less than (Ar ₃-100) ℃, and coiling temperature should be in 500～700 ℃ of scopes.

In next procedure, hot rolled strip carries out pickling, cold rolling and continuous annealing subsequently.As a kind of selection,, after continuous annealing, carry out zinc-plated.For improving the deep drawing quality (r value) of steel plate, cold roling reduction should be at least 70%.Annealing should preferably be carried out in ferritic phase recrystallization temperature scope.And the coating that the present invention uses is not limited to continuous zinc coating.Particularly, even the steel plate that continuous annealing is obtained carries out surface treatment such as phosphoric acid is zinc-plated or electro-galvanizing, can the performance of final steel plate not had problems yet.

The figure according to the first embodiment of the present invention has been represented in Figure 1A～6.In Fig. 3～5, shown in the following Table A of the composition of steel plate and parameter.

Table A The implication of symbol is shown in following table B among Fig. 6.

No. 3 steel samples of table B example 1

(second embodiment)

Describe below according to the use of second embodiment of the invention and add the reason of element, the reason that constituent content is added in restriction, the reason of restriction tensile property and the reason of limit production processing condition.In the explanation hereinafter, " % " expression " weight percent ".

(1) content of interpolation element

C：0.004～0.015％

The carbide that forms together with Nb or Ti influences the work hardening of hanging down the strain zone in the panel forming process, to improving anti-rabbing property contribution is arranged.If C content is lower than 0.004%, can not obtain specific effect.If C content surpasses 0.015%, improve the anti-rabbing property of panel certainly., the panel shape stability suffers damage.Therefore, reach a conclusion and require C content in 0.004 to 0.015% scope.

Si：0.01～0.2％

Silicon can be strengthened steel effectively.Yet,, can not obtain strengthening effect if Si content is lower than 0.01%.On the other hand, if Si content surpasses 0.2%, the surface of steel plate performance suffers damage so.In addition, can produce the surfacial spalling defective after zinc-plated.Therefore, Si content should be in 0.01 to 0.2% scope.

Mn：0.1～1.5％

Mn is used to precipitate sulfide and suppresses thermoplastic deterioration.Mn also can strengthen steel effectively.If Mn content is lower than 0.1%, steel plate can produce red brittleness.Yet if Mn content surpasses 1.5%, steel plate can harden and the shape stability of panel can deterioration so.Therefore, reach a conclusion and require Mn content in 0.1 to 1.5% scope.

P：0.01～0.07％

Phosphorus can be strengthened steel most effectively., if P is lower than 0.01%, P can not show enough reinforcing properties so.On the other hand, if P content surpasses 0.07%, the plasticity of steel plate suffers damage so.Alloying Treatment operation in continuous zinc coating technology can produce defective coating.Therefore, reach a conclusion and require P content in 0.01 to 0.07% scope.

S：0.005～0.015％

If the addition of sulphur surpasses 0.015%, can cause the hot-short of steel so., it is unnecessary with regard to the manufacturing cost of requirement steel plate that S content is lower than 0.005%, because this will carry out desulfurization and degassing processing to molten steel.Therefore, reach a conclusion and require S content in 0.005 to 0.015% scope.

Solid solution attitude Al (Sol.Al): 0.0 1～0.08%

Aluminium is used for steel-deoxidizing.If Al content is lower than 0.01%, so fully deoxidation.On the other hand, if Al content greater than 0.08%, the surface property of steel plate can deterioration so.Therefore, Al content should be in 0.01 to 0.08% scope.

N≤0.005％

Nitrogen is fixed as the form of TiN.Yet, if N content surpasses 0.005%, the reduction of steel plate anti-natural ageing.Nature, N content should not surpass 0.005%.

Nb：0.02～0.12％

Niobium and C are in conjunction with forming tiny carbide particle.These tiny carbide particles influence the work hardening behavior in the panel forming stage, thereby help improving the anti-rabbing property of panel., if Nb content is lower than 0.02%, can not obtain specific effect so.On the other hand, if Nb content surpasses 0.12%, although improved anti-rabbing property so in a way, panel shape stability such as rebound characteristics and surperficial amount of deflection deterioration.Nature, Nb content should be in 0.02 to 0.12% scope.

Ti：0.03～0.1％

Similar with Nb, Ti forms tiny carbide particle.These tiny carbide particles obviously improve the anti-rabbing property of panel., if Ti content is lower than 0.03%, can not obtain specific effect so.On the other hand, if Ti content surpasses 0.1%, the panel shape stability suffers damage.The surface of steel plate galvanized also suffers damage.Nature, Ti should be in 0.03 to 0.1% scope.

-0.001≤C％-(12/93)Nb％-(12/48)Ti ^*≤0.001

Wherein, Ti ^*=Ti%-(48/14) N%-(48/32) S% works as Ti ^*Be not more than at 0 o'clock, think Ti ^*Be 0.

In the present invention, C%-(12/93) Nb%-(12/48) Ti ^*(Ti wherein ^*=Ti%-(48/14) N%-(48/32) S% works as Ti ^*Be not more than at 0 o'clock, think Ti ^*Be 0, by C, Nb, Ti decision.) should be at least-0.001% and be no more than 0.001%.If surpass 0.001%, the anti-natural ageing deterioration.If less than-0.001%, the Ti or the Nb that form sosoloid increase, and infringement surface of steel plate performance increases yield-point, causes the panel shape stability to worsen.

In the present invention, for improving anti-secondary processing brittleness and anti-rabbing property, except above-mentioned interpolation element, require to add the B of following content.

B：0.0001～0.002％

If add B, crystal boundary is strengthened so, and the result has improved the performance of anti-second time of work brittleness.Ferrite crystal grain has also reduced, thereby guarantees the absolute value of yield strength, and improves anti-rabbing property., if B content less than 0.0001%, can not obtain these effects.On the other hand, if B content surpasses 0.002%, yield-point increases so, and the panel shape stability suffers damage.Therefore, reach a conclusion and require B content in 0.0001～0.002% scope.

(2) tensile properties

Exp (ε) * (5.29 * exp (ε)-4.19)≤σ/σ _0.2≤ exp (ε) * (5.64 * exp (ε)-4.49) be 0.002＜ε≤0.096 wherein, and ε represents true strain, σ _0.2Represent 0.2% proof stress, σ represents the true stress with respect to true strain ε.

In the steel plate of the present invention that contains the described interpolation element of aforesaid clause (1), Fe and unavoidable impurities, the flow stress σ that tension test obtains is with respect to 0.2% proof stress σ _0.2Ratio be σ/σ _0.2Between exp (ε) * (5.29 * exp (ε)-4.19) and exp (ε) * (5.64 * exp (ε)-4.49).Wherein, tension test condition is that true strain ε is not less than 0.096 i.e. 0.002＜ε≤0.096 greater than 0.002.

If σ/σ _0.2Be lower than above-mentioned lower limit, the anti-dent load under panel generation 2%P0.1,4%P0.1 and 8%P0.1 condition is up to 160～210N, shown in Fig. 8～10.For measuring anti-dent load, steel formability is a simulated panel as shown in Figure 2, wherein steel plate is applied 2%, 4% or 8% strain also subsequently 170 ℃ of thermal treatments of carrying out 20 minutes.Then, measure the load that makes the remaining displacement of simulated panel generation 0.1mm., if σ/σ _0.2Be lower than above-mentioned lower limit, springback capacity δ (to having 2% strained panel measuring) up to 7～11%, has damaged the panel shape stability so.On the other hand, if σ/σ _0.2Be higher than the above-mentioned upper limit, springback capacity δ is little of 1～5%.Yet anti-rabbing property is low to 140～165N.In other words, can not improve anti-rabbing property.

A kind ofly be suitable as cold-rolled steel sheet and the steel plate galvanized that automobile external panel steel plate is desired, have outstanding panel surface performance and anti-rabbing property, can obtain by control described interpolation elementary composition of aforesaid clause (1) and the described tensile properties of aforesaid clause (2).

This steel plate with property can be according to following method manufacturing.

(3) steel plate manufacturing process

In a first step, smelt the steel of the described composition of aforesaid clause (1).Usually use the converter method to smelt this steel, also can use the electric furnace method to smelt.The molten steel continuous casting becomes slab.Slab after the casting or cooled slab are heated to 1050 ℃ or higher temperature immediately, carry out hot rolling.Hot rolling is carried out under the following conditions: finishing temperature is set at and is not less than (Ar ₃-100) ℃, and coiling temperature is set in 500～700 ℃.If finishing temperature is lower than (Ar ₃-100) ℃, 2%P0.1 (being the anti-dent load of panel when applying 2% strain) is low to 140～155N, as shown in figure 11 so.In other words, can not improve the anti-rabbing property of panel.If coiling temperature is lower than 500 ℃ or be higher than 700 ℃, the 2%P0.1 height promptly reaches 156-175N., near Wca value (i.e. fluctuation is arithmetical av highly, and measurement length is 25mm, selects the mean value of the observed value of 10 points the panel crestal line) is big, in the scope of a value between 0.2 and 0.6 μ m, causes the panel shape stability poor.

In next procedure, hot-rolled steel sheet carries out pickling, cold rolling and continuous annealing subsequently.As a kind of selection, after continuous annealing, carry out zinc-plated.For improving the deep drawing quality of steel plate, cold roling reduction should preferably be at least 70%.Annealing should be carried out in ferritic phase recrystallization temperature scope, but is no more than 930 ℃.And the coating that the present invention uses is not limited to zinc-plated.Particularly, even the steel plate that continuous annealing obtained is carried out surface treatment such as phosphoric acid is zinc-plated or electro-galvanizing, can the performance of final steel plate not had problems yet.

The second embodiment of the present invention has been represented in Fig. 7～17.In Fig. 8～10, the following Table A of the implication of each symbol ' shown in, the implication of symbol is shown in following table B ' among Figure 11.

Table A '

Table B '

No. 8 steel samples of example 1

Describe examples more of the present invention now, the main effect of generation of the present invention is described. Example(example 1)

At the molten steel of composition shown in the prepared in laboratory table 1, continuous casting obtains the bloom slab that thickness is 60mm subsequently.At the steel of the expression of the sample No.1 to 7 shown in the table 1 predetermined component of the present invention, and the steel of sample No.8 to 15 expression Comparative Examples.Bloom slab utilizes the thickness of blooming mill reduction steel plate to 30mm, under air conditions steel billet is heated 1.5 hours at 1050 ℃ subsequently, is used for hot rolling processing (utilizing roughing mill to carry out).After roughing, carry out finish to gauge at 900 ℃, batch simulation at 630 ℃ subsequently, thereby obtain to have the thick hot-rolled steel sheet of 3mm.Then, hot-rolled steel sheet is carried out pickling, cold rolling subsequently its thickness is reduced to 0.8mm, then handled 90 seconds 840 ℃ of continuous annealings.As a kind of selection, after 840 ℃ of continuous annealings are handled 90 seconds, in the time of 460 ℃, carry out zinc-platedly, then carry out Alloying Treatment at 530 ℃.And, subsequently annealed sheet steel or steel plate galvanized are carried out 1.0% temper rolling processing, so that the sample that preparation is used to test.These samples are used for tension test (test specimens of JIS No.5 is according to the method test of JIS Z 2241 regulation) and are used to test r value, 2%BH amount (method according to JIS G 3135 regulations is tested) and Δ the YPel amounts of recovery of 6 months elongation at yield point of 25 ℃ of storages (behind the sample surfaces dress rolling).Sample also will constitute simulated panel shown in Figure 2 (being shaped) under three levels of formation 2,4,8% strained.After 20 minutes, check the anti-rabbing property of panel and the shape stability of panel 170 ℃ of thermal treatments.Anti-rabbing property is estimated under the condition of the remaining displacement (in the explanation, 2%P0.1,4%P0.1 and 8%P0.1 represent that respectively panel has 2,4,6% strain hereinafter) of i.e. panel generation 0.1mm under the load of P0.1.On the other hand, the panel shape stability is utilized springback capacity δ and fluctuation height arithmetical av Wca (JIS B 0610) expression.Radius of curvature R when springback capacity δ utilizes panel to produce 2% strain ' and the pressing mold radius of curvature R define, promptly δ be defined as (R '/R-1) * 100.Here δ is not more than 6%, i.e. δ≤6%, and evaluation result is labeled as zero.Here δ is 7～10%, i.e. δ=7～10%, and evaluation result is labeled as △.Here δ is greater than 10%, i.e. δ＞10%, and evaluation result is labeled as *.On the other hand, for the surface wave height, each has length 25mm, select 10 position measurements near the crestal line of panel, and its average measurement value is expressed as Wca.Here Wca is not more than 0.2 μ m, i.e. Wca≤0.2 μ m, and evaluation result is labeled as zero.Here Wca is greater than 0.2 μ m but be not more than 0.4 μ m, i.e. 0.2 μ m＜Wca≤0.4 μ m, and evaluation result is labeled as △.Here Wca is greater than 0.4 μ m but be not more than 0.6 μ m, i.e. 0.4 μ m＜Wca≤0.6 μ m, and evaluation result is labeled as *.

Table 2 expression is measured and evaluation result.In sample No.1～7, all in the scope of the present invention's regulation, unit elongation El is up to 41.6～45.0% for each composition.Average r value, i.e. (r0+2r45+r90)/4 are up to 1.80～2.20.The Δ YPel of any sample of the present invention is 0%.On the other hand, springback capacity δ and fluctuation height Wca are also very little, are respectively 3-5% and 0.09 μ m～0.17 μ m, guarantee good panel shape stability.And the anti-rabbing property P0.1 when panel has 2%, 4%, 8% strain is up to 158N-193N.

On the other hand, in steel sample No.8～15, each composition not in the scope of the present invention's regulation, can not satisfy plasticity, shape stability and anti-rabbing property simultaneously.Particularly, each in comparative sample No.8～9 shows 2%BH up to 33～42MPa, and Δ YPel is 0.9%-2.2%, shows that these comparative sample do not satisfy anti-natural ageing.Find that also anti-rabbing property P0.1 is 165N-193N when the 2%-8% strain, show to have high anti-rabbing property.Yet each comparative sample unit elongation El and r value are low, and springback capacity δ and Wca are big, show that these comparative sample do not satisfy plasticity and shape stability requirement.Compared steel sample No.10 unit elongation El and r value are high, and springback capacity δ and Wca are low, show that these samples satisfy the requirement of plasticity and shape stability., anti-rabbing property load p 0.1 is reduced to 148N-172N when the 2%-8% strain.The σ of compared steel sample No.11 _0.2Up to 265-270MPa, show that the anti-rabbing property of sample meets the demands.Yet the springback capacity δ and the Wca of these steel samples are big, show that the shape stability of these samples is poor.And the unit elongation El and the r value of these steel samples are low.In compared steel sample No.12～13 each shows high r value, and promptly 2.02～2.20, but El is low by promptly 35.8～36.8%.And these steel samples σ _0.2Up to 240-250MPa, show and satisfy the anti-rabbing property requirement.Yet the springback capacity δ and the Wca of these steel samples are big, show that the shape stability of these compared steel samples does not meet the demands.The unit elongation El of each in compared steel sample No.14～15 is low, and promptly 37.0～38.5%, and the r value is low, promptly 1.51～1.69, show that the shape stability of these samples is poor.

Table 1

The steel sample numbering	????C	????Si	????Mn	????P	????S	??sol.Al
							????1	??0.0067	?0.02	?0.30	??0.040	??0.008	??0.060
????2	??0.0080	?0.06	?0.65	??0.020	??0.012	??0.035
							????3	??0.0085	?0.14	?0.55	??0.050	??0.01	??0.059
????4	??0.013	?0.07	?1.20	??0.020	??0.009	??0.070
							????5	??0.010	?0.13	?0.90	??0.055	??0.011	??0.062
????6	??0.0072	?0.02	?0.80	??0.025	??0.01	??0.040
							????7	??0.011	?0.04	?0.60	??0.040	??0.013	??0.030
????8	??0.0045 *	?0.05	?0.65	??0.055	??0.01	??0.063
							????9	??0.0081	?0.03	?0.45	??0.064	??0.0075	??0.055
????10	??0.0033 *	?0.05	?0.55	??0.035	??0.007	??0.059
							????11	??0.019 *	?0.10	?0.75	??0.060	??0.012	??0.070
????12	??0.0076	?0.06	?0.52	??0.042	??0.009	??0.040
							????13	??0.010	?0.05	?0.80	??0.039	??0.01	??0.040
????14	??0.0070	?0.04	?0.59	??0.015	??0.008	??0.037
							????15	??0.010	?0.05	?0.80	??0.040	??0.01	??0.038

^*: outside the scope of the invention, (continue)

Table 1

The steel sample numbering	????N	????Nb	????B	????O	??(12/93) *??(Nb/C)	Remarks
							????1	??0.0022	??0.062	????tr.	??0.0020	????1.2	The present invention
????2	??0.0030	??0.081	????tr.	??0.0024	????1.3	The present invention
							????3	??0.0020	??0.145	????tr.	??0.0022	????2.2	The present invention
????4	??0.0035	??0.141	????tr.	??0.0017	????1.4	The present invention
							????5	??0.0018	??0.202	????tr.	??0.0019	????2.6	The present invention
????6	??0.0025	??0.073	?0.0003	??0.0025	????1.3	The present invention
							????7	??0.0019	??0.119	?0.0008	??0.0020	????1.4	The present invention
????8	??0.0025	??0.024	????tr.	??0.0019	????0.7 *	Comparative Examples
							????9	??0.0022	??0.050	????tr.	??0.0025	????0.8 *	Comparative Examples
????10	??0.0025	??0.038 *	????tr.	??0.0023	????1.5	Comparative Examples
							????11	??0.0030	??0.191	????tr.	??0.0022	????1.3	Comparative Examples
????12	??0.0025	??0.200	????tr.	??0.0017	????3.4 *	Comparative Examples
							????13	??0.0024	??0.270 *	????tr.	??0.0018	????3.5 *	Comparative Examples
????14	??0.0032	??0.0?81	????tr.	??0.0036 *	????1.5	Comparative Examples
							????15	??0.0024	??0.100	????tr.	??0.0043 *	????1.3	Comparative Examples

^*: outside the scope of the invention

Table 2

The steel sample numbering	Method for annealing	??σ0.2 ??(MPa)	????TS ??(MPa)	????El ????(％)	Average r value	??2％BH ??(MPa)	??ΔYPel ????(％)	??σ(ε＝0.02) ????(MPa)	??σ(ε＝0.04) ????(MPa)
										????1	????CA	????225	????373	??42.5	????1.88	????0	????0	????283	????318
????CG	????227	????370	??42.0	????1.85	????0	????0	????286	????322
									????2		????CA	????229	????377	??43.0	????1.95	????0	????0	????289	????324
????CG	????230	????375	??42.6	????1.92	????0	????0	????289	????324
										????3	????CA	????235	????388	??45.0	????2.20	????0	????0	????294	????328
????CG	????232	????390	??44.6	????2.10	????0	????0	????294	????327
									????4		????CA	????233	????396	??42.0	????1.97	????0	????0	????293	????328
????CG	????230	????392	??41.6	????1.93	????0	????0	????293	????323
										????5	????CA	????230	????370	??42.5	????2.15	????0	????0	????288	????321
????CG	????230	????375	??42.0	????2.11	????0	????0	????286	????320
									????6		????CA	????235	????380	??42.0	????2.00	????0	????0	????298	????328
????CG	????233	????376	??41.6	????1.94	????0	????0	????293	????324
										????7	????CA	????233	????385	??43.0	????1.99	????0	????0	????295	????323
????CG	????225	????380	??42.0	????1.93	????0	????0	????284	????316

^*CA outside formula (1) scope: continuous annealing CG: continuous zinc coating (continuing)

Table 2

The steel sample numbering	Method for annealing	??σ0.2 ??(MPa)	????TS ??(MPa)	????El ????(％)	Average r value	??2％BH ??(MPa)	??ΔYPel ????(％)	??σ(ε＝0.02) ????(MPa)	??σ(ε＝0.04) ????(MPa)
										????8	????CA	????240	????343	??41.0	????1.70	????35	????1.0	????270 *	????296 *
????CG	????245	????345	??39.7	????1.65	????33	????0.9	????276 *	????300 *
									????9		????CA	????260	????399	??36.5	????1.55	????4?0	????2.0	????290 *	????315 *
????CG	????258	????402	??35.9	????1.51	????42	????2.2	????290 *	????311 *
										????10	????CA	????213	????358	??43.5	????2.00	????0	????0	????280 *	????312 *
????CG	????210	????357	??43.0	????1.97	????0	????0	????272 *	????305 *
									????11		????CA	????270	????410	??38.0	????1.60	????0	????0	????320 *	????363 *
????CG	????265	????404	??37.5	????1.57	????0	????0	????313 *	????357 *
										????12	????CA	????244	????386	??36.8	????2.20	????0	????0	????304	????339
????CG	????240	????385	??36.0	????2.10	????0	????0	????299	????335
									????13		????CA	????247	????400	??36.3	????2.15	????0	????0	????307	????340
????CG	????250	????402	??35.8	????2.02	????0	????0	????310	????345
										????14	????CA	????228	????370	??38.5	????1.69	????0	????0	????288	????319
????CG	????225	????368	??38.2	????1.65	????0	????0	????282	????319
									????15		????CA	????255	????406	??37.0	????1.60	????0	????0	????307 *	????342 *
????CG	????258	????404	??37.5	????1.51	????0	????0	????304 *	????344 *

^*CA outside formula (1) scope: continuous annealing CG: continuous zinc coating (continuing)

Table 2

The steel sample numbering	??σ(ε＝0.08) ????(MPa)	??2％PO.1 ????(N)	??4％PO.1 ????(N)	??8％PO.1 ????(N)	??δ(％)	Wca(μm)	Remarks
								????1	????385	????158	????167	????183	?3(○)	0.10(○)	The present invention
????389	????159	????168	????186	?3(○)	0.10(○)	The present invention
							????2		????387	????160	????171	????186	?4(○)	0.10(○)	The present invention
????389	????160	????171	????189	?4(○)	0.15(○)	The present invention
								????3	????397	????163	????173	????192	?5(○)	0.17(○)	The present invention
????392	????163	????173	????190	?4(○)	0.14(○)	The present invention
							????4		????392	????163	????175	????191	?3(○)	0.15(○)	The present invention
????388	????161	????170	????189	?3(○)	0.14(○)	The present invention
								????5	????390	????160	????171	????190	?3(○)	0.10(○)	The present invention
????388	????160	????169	????190	?3(○)	0.13(○)	The present invention
							????6		????395	????167	????175	????193	?4(○)	0.15(○)	The present invention
????392	????164	????173	????189	?4(○)	0.12(○)	The present invention
								????7	????390	????164	????174	????188	?4(○)	0.12(○)	The present invention
????383	????159	????168	????184	?3(○)	0.09(○)	The present invention
							????8		????355 *	????166	????170	????185	?7(△)	0.26(△)	Comparative Examples
????361 *	????165	????172	????188	?8(△)	0.30(△)	Comparative Examples

^*Outside formula (1) scope

CA: continuous annealing CG: continuous zinc coating (continuing)

Table 2

The steel sample numbering	??σ(ε＝0.08) ????(MPa)	2％PO.1 ????(N)	4％PO.1 ????(N)	??8％PO.1 ????(N)	??δ(％)	Wca(μm)	Remarks
								????9	????374 *	????178	????190	????193	??11(×)	0.50(×)	Comparative Examples
????372 *	????180	????187	????193	??11(×)	0.49(×)	Comparative Examples
							????10		????377 *	????154	????160	????172	??2(○)	0.10(○)	Comparative Examples
????373 *	????148	????157	????170	??2(○)	0.08(○)	Comparative Examples
								????11	????419 *	????182	????197	????196	??12(×)	0.46(×)	Comparative Examples
????415 *	????177	????195	????190	??11(×)	0.44(×)	Comparative Examples
							????12		????408	????168	????177	????189	??7(△)	0.25(△)	Comparative Examples
????405	????166	????173	????188	??7(△)	0.24(△)	Comparative Examples
								????13	????416	????168	????175	????191	??8(△)	0.29(△)	Comparative Examples
????419	????171	????181	????194	??10(△)	0.29(△)	Comparative Examples
							????14		????388	????161	????159	????190	??3(○)	0.12(○)	Comparative Examples
????382	????158	????160	????187	??3(○)	0.10(○)	Comparative Examples
								????15	????416 *	????166	????174	????191	??11(×)	0.27(△)	Comparative Examples
????415 *	????165	????177	????190	??11(×)	0.32(△)	Comparative Examples

^*CA outside formula (1) scope: continuous annealing CG: continuous zinc coating (example 2)

At the molten steel of the No.2 steel sample composition of the present invention shown in the prepared in laboratory table 1, continuous casting obtains the bloom slab that thickness is 50mm subsequently.Steel billet utilizes thickness that blooming mill reduces steel plate to 25mm, subsequently under air conditions with steel plate 1250 ℃ of heating 1 hour, carry out subsequently hot rolling processing with the thickness of reduction hot-rolled steel sheet to 2.8mm.Finishing temperature in hot rolling is handled and coiling temperature change in the temperature range of 770～930 ℃ and 450～750 ℃ respectively.Then, hot-rolled steel sheet carries out pickling, subsequently with the cold rolling 0.75mm that is reduced to of its thickness, then handles 90 seconds 825 ℃ of insulations.And subsequently steel plate being carried out unit elongation is the processing of 1.2% temper rolling.So the steel-sheet mechanical property of preparation and panel performance resemble and test the example 1.Its result of table 3 expression.The finishing temperature of each in No.1 of the present invention～3 steel samples is lower than (Ar ₃-100) ℃.In these steel samples each shows the low P0.1 value under the 2%-8% strain, i.e. 139N-159N, and high Wca value i.e. 0.35 μ m～0.4 μ m, and this shows that the anti-rabbing property of these steel samples and shape stability are poor.And the r value of these steel samples is low to 1.69～1.77.The coiling temperature of each in No.7 and 12 steel samples is lower than 500 ℃.In these steel samples each shows high σ respectively _0.2Be 243-248MPa, show to have good anti-rabbing property.Yet the springback capacity δ of these steel samples is up to 8%, and Wca shows that up to 0.3 μ m the panel shape stability of these steel samples is poor.The coiling temperature of each in No.11,15 and 18 steel samples is higher than 700 ℃.In these steel samples each shows low σ _0.2, i.e. 210-216MPa, and low δ value, promptly 2%.Yet its Wca is up to 0.42～0.43 μ m.The anti-rabbing property load of these steel samples is also low.On the other hand, each among steel sample No.4-6, the 8-10,13,14,16 and 17 finds that aspect finishing temperature and the coiling temperature all in the scope in the present invention regulation its plasticity, anti-rabbing property and shape stability all meet the demands.

Table 3

?No.	The steel sample numbering	Finishing temperature (℃)	Coiling temperature (℃)	??σ0.2 ??(MPa)	????TS ??(MPa)	????El ????(％)	Average r value		????σ(ε＝0.02) ????(MPa)
										????1	Steel 2	????770 **	????540	????212	????375	??41.3	????1.73		????275 *
????2	????600	????217	????372	??42.0	????1.69		????281 *
								????3	????660	????215			????370	??42.0	????1.77		????280 *
????4	????810	????530	????230	????380	??43.0	????1.89												????289
								????5	????600	????227		????375	??43.5	????1.92		????285
????6		????670	????225	????377	??44.0	????1.95											????285
								????7	????850	????470 **		????243	????382	??41.0	????1.80			????293 *
????8	????530	????232	????377	??42.8	????1.88		????292
								????9		????590		????230	????370	??43.3	????1.93		????289
???10	????650	????230	????373	??43.0	????1.95		????293
								???11		????715 **		????216	????370	??43.3	????1.82		????281 *
???12	????890	????450 **	????248	????382	??41.2	????1.82												????301 *
								???13	????550	????233		????371	??42.8	????1.90		????292
???14		????650	????226	????378	??43.5	????1.98											????287
								???15	????750 **	????210		????367	??42.7	????1.83		????274 *
???16		????930	????550	????230	????370	??42.8	????1.91										????290
	???17								????650	????225		????375	??43.2	????1.95		????283
???18			????750 **	????212	????368	??43.7	????1.81										????277 *

(continuing)

Table 3

??No.	??σ(ε＝0.04) ????(MPa)	??σ(ε＝0.08) ????(MPa)	??2％，4％，8％P0.1 ????(N)	????δ ????(％)	????Wca ????(μm)	Remarks
							????1	????306 *	????375 *	????139-153	?2(○)	0.35(△)	Comparative Examples
????2	????313 *	????383 *	????143-159	?2(○)	0.40(△)	Comparative Examples
							????3	????311 *	????380 *	????144-156	?2(○)	0.40(△)	Comparative Examples
????4	????322	????392	????152-179	?4(○)	0.15(○)	The present invention
							????5	????317	????387	????150-175	?4(○)	0.10(○)	The present invention
????6	????318	????388	????150-177	?3(○)	0.09(○)	The present invention
							????7	????328 *	????400 *	????155-182	?8(△)	0.30(△)	Comparative Examples
????8	????324	????392	????154-178	?4(○)	0.10(○)	The present invention
							????9	????320	????390	????151-178	?4(○)	0.12(○)	The present invention
????10	????322	????392	????154-177	?4(○)	0.12(○)	The present invention
							????11	????313 *	????382 *	????144-156	?2(○)	0.43(×)	Comparative Examples
????12	????334 *	????407 *	????160-184	?8(△)	0.30(△)	Comparative Examples
							????13	????325	????394	????155-180	?4(○)	0.07(○)	The present invention
????14	????321	????385	????153-171	?3(○)	0.18(○)	The present invention
							????15	????305 *	????372 *	????139-152	?2(○)	0.42(×)	Comparative Examples
????16	????321	????390	????152-178	?4(○)	0.18(○)	The present invention
							????17	????315	????384	????150-170	?3(○)	0.17(○)	The present invention
????18	????309 *	????377 *	????142-155	?2(○)	0.42(×)	Comparative Examples

^*: outside formula (1) scope ^*: outside the scope of the invention (example 3)

At the molten steel (No.1 to the 15 expression example of the present invention in the table 4, and the steel of example No.16 to 29 expression Comparative Examples) of composition shown in the prepared in laboratory table 4, continuous casting obtains the bloom slab that thickness is 60mm subsequently.Bloom slab utilizes the thickness of blooming mill reduction steel plate to 30mm, under air conditions steel billet is heated 1 hour at 1100 ℃ subsequently, carries out hot rolling processing (utilizing roughing mill to carry out).After roughing, carry out finish to gauge at 890 ℃, batch simulation at 600 ℃ subsequently, thereby obtain to have the thick hot-rolled steel sheet of 3mm.Then, hot-rolled steel sheet carries out pickling, subsequently with the cold rolling 0.75mm that is reduced to of its thickness, then handles 90 seconds 850 ℃ of continuous annealings.As a kind of selection, after 850 ℃ of continuous annealings are handled 90 seconds, in the time of 460 ℃, carry out zinc-platedly, then carry out Alloying Treatment at 500 ℃.And, subsequently annealed sheet steel or steel plate galvanized are carried out 1.0% temper rolling processing, with preparation test sample.These samples are used for tension test (test specimens of JISNo.5 is according to the method test of JIS Z 2241 regulation) and are used to test 2%BH amount (according to the method test of JIS G 3135 regulations) and the Δ YPel amounts of recovery of 6 months elongation at yield point of 25 ℃ of storages (behind the sample surfaces dress rolling).Sample also will constitute simulated panel shown in Figure 7 (is that three levels of 2%, 4%, 8% are molded in strain).After 20 minutes, check the anti-rabbing property of panel and the shape stability of panel 170 ℃ of thermal treatments.Anti-rabbing property is estimated under the load of P0.1 and under the condition of the remaining displacement (in the explanation, 2%P0.1,4%P0.1 and 8%P0.1 represent that respectively panel has 2,4,8% strain hereinafter) of panel generation 0.1mm.On the other hand, the panel shape stability utilizes springback capacity δ and fluctuation height arithmetical av Wca to represent (JIS B0610).Radius of curvature R when springback capacity δ utilizes panel to produce 2% strain ' and the pressing mold radius of curvature R define, promptly δ be defined as (R '/R-1) * 100.Here δ is not more than 6%, i.e. δ≤6%, and evaluation result is labeled as zero.Here δ is 7～10%, i.e. δ=7～10%, and evaluation result is labeled as △.Here δ is greater than 10%, i.e. δ＞10%, and evaluation result is labeled as *.On the other hand, for the surface wave height, each has length 25mm, select 10 position measurements according to the method for JIS B0610 regulation near the crestal line of panel, and its average measurement value is expressed as Wca.Here Wca is not more than 0.2 μ m, i.e. Wca≤0.2 μ m, and evaluation result is labeled as zero.Here Wca is greater than 0.2 μ m but be not more than 0.4 μ m, i.e. 0.2 μ m＜Wca≤0.4 μ m, and evaluation result is labeled as △.Here Wca is greater than 0.4 μ m but be not more than 0.6 μ m, i.e. 0.4 μ m＜Wca≤0.6 μ m, and evaluation result is labeled as *.

Table 5 expression is measured and evaluation result.In sample No.1～15, all in the scope of the present invention's regulation, the 2%BH amount is 0 to 26MPa to each composition, and Δ YPel is 0.The C content of comparative example No.16 be 0.0025% and 2%BH amount be 36-38MPa, and the 2%P0.1 of steel sample of the present invention, 4%P0.1 and 8%P0.1 to want height be 150-180N, 160-192N and 175-208N, show that steel plate has high anti-rabbing property.Because δ≤6% (evaluation result is labeled as zero) and Wca＜0.2 μ m (evaluation result is labeled as zero), steel sample of the present invention also satisfies the requirement of panel shape stability.For having measured the amount of recovery Δ YPel that yield-point prolongs through surperficial softening annealing at 25 ℃ of samples (steel sample No.6 of the present invention and Comparative Examples steel sample 18) that store 18 months, its result is illustrated among Figure 12.The Δ YPel value that steel sample No.6 of the present invention stored after 18 months is lower than 0.2%, shows to have outstanding anti-natural ageing.On the other hand, the Δ YPel value of Comparative Examples steel sample No.18 shows that greater than 2.2% its anti-natural ageing obviously worsens.

Steel sample Comparative Examples No.16-29 does not within the scope of the present invention show high 2%P0.1,4%P0.1 respectively and 8%P0.1 is 140-195N, 151-202N and 160-213N, shows that steel plate has high anti-rabbing property.Yet, Comparative Examples steel sample No.16,18,19,23,24 and 29, the 2%BH amount is 33-45MPa, it is Δ YPel 〉=0.2% that Δ YPel value is not less than 0.2%, and Wca is Wca＞0.2% greater than 0.2 μ m.In other words, the Comparative Examples steel sample is poorer than the anti-natural ageing and the panel forming of the present invention steel sample.The Δ YPel value of Comparative Examples steel sample No.17,20-22 and 25-28 is 0, shows to have satisfied anti-natural ageing., the springback capacity δ of the steel sample of these Comparative Examples is not less than 7%, and promptly δ 〉=7% shows that these steel samples do not have satisfied panel shape stability.

Table 4

The steel sample numbering	Chemical Composition (% weight percent)
									????C	????Si	??Mn	????P	????S	?sol.Al	????N	????Nb
	????1	??0.0044	??0.015	??0.31	??0.04	??0.007	??0.06	??0.0025									??0.04
????2									??0.0072	??0.06	??0.67	??0.02	??0.012	??0.035	??0.003	??0.062
	????3	??0.0088	??0.14	??0.55	??0.05	??0.009	??0.059	??0.0022									??0.072
????4									??0.013	??0.08	??1	??0.015	??0.009	??0.07	??0.0035	??0.097
	????5	??0.01	??0.17	??0.9	??0.055	??0.011	??0.062	??0.004									??0.077
????6									??0.0066	??0.075	??1.2	??0.045	??0.008	??0.042	??0.0018	??0.046
	????7	??0.011	??0.053	??0.85	??0.033	??0.013	??0.025	??0.0027									??0.08
????8									??0.0059	??0.01	??0.75	??0.06	??0.01	??0.055	??0.0044	??0.042
	????9	??0.0071	??0.065	??0.8	??0.045	??0.011	??0.059	??0.0019									??0.05
????10									??0.005	??0.035	??0.97	??0.035	??0.0065	??0.04	??0.0027	??tr.
	????11	??0.0095	??0.04	??0.69	??0.05	??0.012	??0.053	??0.0032									??tr.
????12									??0.0066	??0.02	??1.3	??0.039	??0.009	??0.037	??0.002	??tr.
	????13	??0.0088	??0.1	??0.73	??0.02	??0.01	??0.04	??0.0025									??0.062
????14									??0.0055	??0.062	??0.52	??0.03	??0.008	??0.051	??0.0024	??0.02
	????15	??0.01	??0.049	??0.33	??0.061	??0.012	??0.069	??0.003									??tr.

(continuing)

Table 4

The steel sample numbering	Chemical Composition (% weight percent)
									????C	????Si	????Mn	????P	????S	?sol.Al	????N	????Nb
	????16	??0.0025 *	??0.05	??0.65	??0.055	??0.01	??0.063	??0.0025									??0.01 *
????17									??0.003 *	??0.05	??0.55	??0.035	??0.007	??0.059	??0.0025	??0.02
	????18	??0.005	??0.1	??0.75	??0.06	??0.012	??0.07	??0.003									??0.026
????19									??0.0085	??0.08	??1	??0.051	??0.008	??0.037	??0.0037	??0.05
	????20	??0.01	??0.05	??0.8	??0.039	??0.01	??0.04	??0.0024									??0.1
????21									??0.019 *	??0.03	??0.45	??0.064	??0.0075	??0.055	??0.0022	??0.15 *
	????22	??0.0055	??0.07	??0.7	??0.05	??0.01	??0.049	??0.003									??0.027
????23									??0.011	??0.055	??0.59	??0.04	??0.01	??0.045	??0.002	??0.056
	????24	??0.006	??0.1	??0.73	??0.046	??0.0085	??0.065	??0.0032									??tr.
????25									??0.02 *	??0.065	??1.2	??0.035	??0.011	??0.052	??0.0025	??tr.
	????26	??0.0049	??0.1	??0.82	??0.05	??0.007	??0.056	??0.0024									??tr. *
????27									??0.009	??0.045	??0.85	??0.05	??0.01	??0.07	??0.0029	??tr. *
	????28	??0.0055	??0.08	??0.7	??0.05	??0.009	??0.052	??0.002									??tr. *
????29									??0.009	??0.04	??0.5	??0.038	??0.01	??0.059	??0.0026	??tr. *

Annotate: symbol ^*The expression value is not in the scope of the present invention's regulation

Ti ^*＝Ti％-(48/14)N％-(48/32)S％

(Ti wherein ^*Be not more than at 0 o'clock, think Ti ^*Be 0) (continuing)

Table 4

The steel sample numbering	Chemical Composition (% weight percent)				???C-(12/93)Nb- ???(12/48)Ti *	Remarks
							????Ti	????Zr	????V	????B
	????1	????tr.	????tr.	????tr.							????tr.	????-0.0008	The present invention
????2					????tr.	????tr.	????tr.	????tr.	????-0.0008
	????3	????tr.	????tr.	????tr.						????tr.	????-0.0005
????4					????tr.	????tr.	????tr.	????tr.	????0.0005
	????5	????tr.	????tr.	????tr.						????tr.	????0.0001
????6					????tr.	????tr.	????tr.	????tr.	????0.0007
	????7	????0.025	????tr.	????tr.						????tr.	????0.0007
????8					????0.015	????tr.	????tr.	????tr.	????0.0005
	????9	????0.027	????tr.	????tr.						????tr.	????-0.0003
????10					????0.037	????tr.	????tr.	????tr.	????0.0005
	????11	????0.07	????tr.	????tr.						????tr.	????-0.0008
????12					????0.045	????tr.	????tr.	????tr.	????0.0004
	????13	????tr.	????tr.	????tr.						????0.0003	????0.0008
????14					????0.032	????tr.	????tr.	????0.0013	????0.0000
	????15	????0.067	????tr.	????tr.						????0.0006	????0.0003

Annotate: symbol ^*The expression value is not in the scope of the present invention's regulation

Ti ^*＝Ti％-(48/14)N％-(48/32)S％

(Ti wherein ^*Be not more than at 0 o'clock, think Ti ^*Be 0) (continuing)

Table 4

The steel sample numbering	Chemical Composition (% weight percent)				C-(12/93)Nb- (12/48)Ti *	Remarks
							????Ti	????Zr	????V	????B
	????16	????tr.	????tr.	????tr.							????tr.	0.0012 *	Comparative Examples
????17					????tr.	????tr.	????tr.	????tr.	0.0004
	????18	????tr.	????tr.	????tr.						????tr.	0.0016 *
????19					????tr.	????tr.	????tr.	????tr.	0.0020 *
	????20	????tr.	????tr.	????tr.						????tr.	-0.0029 *
????21					????tr.	????tr.	????tr.	????tr.	-0.0004
	????22	????0.041	????tr.	????tr.						????tr.	-0.0019 *
????23					????0.03	????tr.	????tr.	????tr.	0.0017 *
	????24	????0.041	????tr.	????tr.						????tr.	0.0017 *
????25					????0.12 *	????tr.	????tr.	????tr.	-0.0037
	????26	????tr. *	????0.075 *	????tr.						????tr.	--- *
????27					????tr. *	????0.11 *	????tr.	????tr.	--- *
	????28	????tr. *	????tr.	????0.025 *						????tr.	--- *
????29					????tr. *	????tr.	????0.035 *	????tr.	--- *

Annotate: symbol ^*The expression value is not in the scope of the present invention's regulation

Ti ^*＝Ti％-(48/14)N％-(48/32)S％

(Ti wherein ^*Be not more than at 0 o'clock, think Ti ^*Be 0)

Table 5 (part 1)

The steel sample numbering	Annealing	??σ0.2 ??(MPa)	???TS (MPa)	????El ????(％)	2％BH (MPa)	??ΔYPel ????(％)	??σ(ε＝0.2) ????(MPa)	??σ(ε＝0.04) ????(MPa)	??σ(ε＝0.08) ????(MPa)
										????1	Continuous annealing	????229	????370	??41	????0	????0	????285	????321	????388
Continuous zinc coating	????231	????368	??40	????0	????0	????287	????323	????391
									????2		Continuous annealing	????230	????375	??40.5	????0	????0	????290	????322	????390
Continuous zinc coating	????230	????377	??39.5	????0	????0	????289	????325	????388
										????3	Continuous annealing	????237	????390	??39.3	????0	????0	????296	????331	????403
Continuous zinc coating	????235	????392	??38.5	????0	????0	????299	????330	????400
									????4		Continuous annealing	????230	????380	??39.5	????22	????0	????290	????321	????389
Continuous zinc coating	????228	????383	??38.6	????20	????0	????290	????320	????385
										????5	Continuous annealing	????237	????395	??39	????2	????0	????299	????332	????403
Continuous zinc coating	????238	????397	??38.3	????4	????0	????297	????330	????405

(continuing)

Table 5 (part 1)

The steel sample numbering	Annealing	??σ0.2 ??(MPa)	??TS (MPa)	????El ????(％)	2％BH (MPa)	??ΔYPel ????(％)	??σ(ε＝0.2) ????(MPa)	??σ(ε＝0.04) ????(MPa)	??σ(ε＝0.08) ????(MPa)
										????6	Continuous annealing	????235	????395	??39.3	????24	????0	????296	????328	????398
Continuous zinc coating	????237	????396	??38.1	????25	????0	????299	????330	????396
									????7		Continuous annealing	????235	????385	??40.3	????23	????0	????296	????329	????397
Continuous zinc coating	????237	????385	??39.1	????22	????0	????300	????333	????400
										????8	Continuous annealing	????230	????392	??39	????20	????0	????290	????322	????389
Continuous zinc coating	????233	????393	??38	????20	????0	????295	????325	????392
									????9		Continuous annealing	????235	????387	??39.5	????0	????0	????296	????329	????397
Continuous zinc coating	????237	????385	??38.3	????0	????0	????300	????330	????400
										????10	Continuous annealing	????232	????381	??40	????18	????0	????292	????323	????392
Continuous zinc coating	????235	????384	??38.5	????19	????0	????295	????328	????399

(continuing)

Table 5 (part 1)

The steel sample numbering	?2％P0.1 ????(N)	?4％P0.1 ????(N)	?8％P0.1 ????(N)	????δ ????(％)	????Wca ????(μm)	Remarks
							????1	????150	????160	????175	?4(○)	??0.1(○)	Example of the present invention
????150	????162	????177	?4(○)	??0.11(○)
					????2	????153		????162	????177	?4(○)	??0.1(○)
????152	????163	????175	?4(○)	??0.13(○)
						????3	????156	????166	????186	?5(○)	??0.1(○)
????159	????165	????183	?5(○)	??0.1(○)
					????4		????165	????177	????193	?3(○)	??0.15(○)
????162	????170	????188	?3(○)	??0.14(○)
						????5	????160	????167	????188	?5(○)	??0.09(○)
????160	????167	????190	?5(○)	??0.13(○)
					????6		????176	????186	????205	?4(○)	??0.15(○)
????180	????188	????205	?4(○)	??0.16(○)
						????7	????175	????186	????203	?4(○)	??0.17(○)
????178	????188	????205	?4(○)	??0.15(○)
					????8		????163	????175	????190	?3(○)	??0.15(○)
????170	????179	????195	?4(○)	??0.15(○)
						????9	????156	????163	????181	?4(○)	??0.08(○)
????159	????165	????183	?4(○)	??0.12(○)
					????10		????163	????173	????191	?3(○)	??0.1(○)
????169	????181	????200	?4(○)	??0.08(○)

Table 5 (part 2)

The steel sample numbering	Annealing	??σ0.2 ??(MPa)	????TS (MPa)	????El ????(％)	2％BH (MPa)	ΔYPel ????(％)	??σ(ε＝0.2) ????(MPa)	??σ(ε＝0.04) ????(MPa)	??σ(ε＝0.08) ????(MPa)
										????11	Continuous annealing	????237	????395	????39.3	????0	????0	????298	????331	????401
Continuous zinc coating	????236	????394	????38.4	????0	????0	????296	????330	????398
									????12		Continuous annealing	????235	????387	????40	????17	????0	????296	????330	????397
Continuous zinc coating	????236	????389	????39.8	????18	????0	????300	????330	????400
										????13	Continuous annealing	????237	????378	????40	????26	????0	????297	????333	????401
Continuous zinc coating	????235	????380	????39.5	????24	????0	????293	????330	????391
									????14		Continuous annealing	????233	????380	????41	????0	????0	????296	????325	????392
Continuous zinc coating	????235	????382	????40.6	????0	????0	????294	????330	????397
										????15	Continuous annealing	????238	????398	????39	????15	????0	????303	????336	????405
Continuous zinc coating	????237	????395	????38.2	????16	????0	????303	????331	????402

(continuing)

Table 5 (part 2)

The steel sample numbering	Annealing	??σ0.2 ??(MPa)	????TS (MPa)	????El ????(％)	2％BH (MPa)	??ΔYPel ????(％)	??σ(ε＝0.2) ????(MPa)	??σ(ε＝0.04) ????(MPa)	??σ(ε＝0.08) ????(MPa)
										????16	Continuous annealing	????236	????355	????43	????36 *	????0.6 *	????268 *	????293 *	????352 *
Continuous zinc coating	????235	????356	????42	????38 *	????0.5 *	????267 *	????291 *	????351 *
									????17		Continuous annealing	????242	????368	????41.5	????15	????0	????267 *	????295 *	????357 *
Continuous zinc coating	????244	????370	????40	????13	????0	????273 *	????310 *	????366 *
										????18	Continuous annealing	????245	????390	????39	????37 *	????0.7 *	????294 *	????318 *	????385 *
Continuous zinc coating	????245	????393	????38	????39 *	????0.6 *	????295 *	????318 *	????388 *
									????19		Continuous annealing	????258	????400	????38.2	????44 *	????2 *	????310 *	????343 *	????405 *
Continuous zinc coating	????255	????403	????37	????45 *	????1.8 *	????308 *	????337 *	????409 *
										????20	Continuous annealing	????256	????408	????38	????0	????0	????310 *	????345 *	????417 *
Continuous zinc coating	????260	????405	????37.2	?????0	????0	????315 *	????344 *	????413 *

Annotate: symbol ^*The expression value is not in the scope of the present invention's regulation (continuing)

Table 5 (part 2)

The steel sample numbering	??2％P0.1 ????(N)	?4％P0.1 ????(N)	?8％P0.1 ????(N)	????δ ????(％)	????Wca ????(μm)	Remarks
							????11	????158	????166	????185	????6(○)	????0.13(○)	Example of the present invention
????156	????165	????181	????5(○)	????0.1(○)
					????12	????168		????181	????197	????5(○)	????0.15(○)
????173	????183	????200	????5(○)	????0.14(○)
						????13	????179	????192	????208	????6(○)	????0.17(○)
????172	????187	????199	????5(○)	????0.18(○)
					????14		????156	????163	????178	????4(○)	????0.12(○)
????155	????165	????181	????5(○)	????0.1(○)
						????15	????173	????185	????203	????6(○)	????0.15(○)
????175	????181	????200	????6(○)	????0.15(○)
					????16		????160	????165	????177	????5(○)	????0.26(△)	Comparative Examples
????161	????165	????179	????5(○)	????0.285(△)
						????17	????140	????151	????165	????8(△)	????0.15(○)
????142	????152	????160	????8(△)	????0.16(○)
					????18		????183	????188	????205	????9(△)	????0.25(△)
????185	????190	????208	???10(△)	????0.26(△)
						????19	????193	????202	????210	???13(×)	????0.39(△)
????195	????200	????212	???12(×)	????0.42(×)
					????20		????163	????179	????199	???12(×)	????0.19(○)
????170	????178	????195	???14(×)	????0.25(△)

Table 5 (part 3)

The steel sample numbering	Annealing	??σ0.2 ??(MPa)	??TS (MPa)	????El ????(％)	2％BH (MPa)	??ΔYPel ????(％)	??σ(ε＝0.2) ????(MPa)	??σ(ε＝0.04) ????(MPa)	??σ(ε＝0.08) ????(MPa)
										????21	Continuous annealing	????268	????410	????38	????0	????0	????320 *	????363 *	????421 *
Continuous zinc coating	????260	????415	????37	????0	????0	????310 *	????345 *	????409 *
									????22		Continuous annealing	????256	????391	????39	????0	????0	????308 *	????344 *	????410 *
Continuous zinc coating	????251	????393	????40	????0	????0	????303 *	????332 *	????400 *
										????23	Continuous annealing	????261	????400	????38.4	????40 *	????0.8 *	????308 *	????347 *	????415 *
Continuous zinc coating	????263	????403	????37.2	????37 *	????1.2 *	????310 *	????343 *	????420 *
									????24		Continuous annealing	????257	????394	????39	????40 *	????0.6 *	????309 *	????347 *	????415 *
Continuous zinc coating	????262	????391	????38.2	????37 *	????1 *	????312 *	????343 *	????416 *
										????25	Continuous annealing	????265	????398	????38.3	????0	????0	????312 *	????350 *	????416 *
Continuous zinc coating	????268	????403	????37.1	????0	????0	????319 *	????351 *	????422 *

Annotate: symbol ^*The expression value is not in the scope of the present invention's regulation (continuing)

Table 5 (part 3)

The steel sample numbering	Annealing	??σ0.2 ??(MPa)	?TS (MPa)	????El ????(％)	2％BH (MPa)	ΔYPel ??(％)	??σ(ε＝0.2) ????(MPa)	??σ(ε＝0.04) ????(MPa)	??σ(ε＝0.08) ????(MPa)
										????26	Continuous annealing	????258	????393	????38.7	????0	????0	????308 *	????340 *	????407 *
Continuous zinc coating	????258	????390	????37	????0	????0	????308 *	????341 *	????410 *
									????27		Continuous annealing	????265	????400	????38.3	????22	????0	????313 *	????345 *	????412 *
Continuous zinc coating	????268	????403	????37.1	????20	????0	????320 *	????350 *	????420 *
										????28	Continuous annealing	????237	????399	????39.3	????18	????0	????310 *	????345 *	????419 *
Continuous zinc coating	????239	????400	????38	????15	????0	????315 *	????345 *	????422 *
									????29		Continuous annealing	????258	????388	????38.5	????35 *	????0.4 *	????304 *	????347 *	????403 *
Continuous zinc coating	????260	????391	????37.1	????33 *	????0.7 *	????308 *	????343 *	????407 *

Annotate: symbol ^*The expression value is not in the scope of the present invention's regulation (continuing)

Table 5 (part 3)

The steel sample numbering	?2％P0.1 ????(N)	??4％P0.1 ????(N)	8％P0.1 ????(N)	????δ ????(％)	????Wca ????(μm)	Remarks
							????21	????176	????193	????194	??14(×)	??0.42(×)	Comparative Examples
????163	????180	????190	??14(×)	??0.4(△)
					????22	????162		????178	????191	??12(×)	??0.25(△)
????160	????167	????183	??12(×)	??0.27(△)
						????23	????188	????202	????212	??13(×)	??0.49(×)
????186	????199	????213	??13(×)	??0.44(×)
					????24		????190	????202	????212	??12(×)	??0.23(△)
????188	????199	????211	??13(×)	??0.25(△)
						????25	????163	????184	????200	??13(×)	??0.43(×)
????175	????185	????205	??14(×)	??0.45(×)
					????26		????162	????170	????189	??11(×)	??0.36(△)
????162	????173	????190	??13(×)	??0.35(△)
						????27	????185	????195	????208	??13(×)	??0.4(△)
????185	????197	????208	??14(×)	??0.52(×)
					????28		????181	????193	????207	??7(△)	??0.59(×)
????183	????192	????207	??8(△)	??0.55(×)
						????29	????184	????200	????206	??12(×)	??0.44(×)
????185	????198	????208	??13(×)	??0.53(×)

(example 4)

At the molten steel of No.2 of the present invention shown in the prepared in laboratory table 4 and 14 sample compositions, continuous casting obtains the steel billet that thickness is 50mm subsequently.Steel billet utilizes thickness that blooming mill reduces steel plate to 20mm, subsequently under air conditions with steel billet 1200 ℃ of heating 1 hour, carry out hot rolling processing and the thickness of reduction hot-rolled steel sheet to 2.8mm.Finishing temperature in hot rolling is handled and coiling temperature change in the temperature range of 750～930 ℃ and 440～750 ℃ respectively.Then, hot-rolled steel sheet carries out pickling, cold rolling subsequently its thickness is reduced to 0.75mm, then 800 ℃ of continuous annealings (insulation is handled) 90 seconds.And, subsequently steel plate is carried out the processing of (1.4%) temper rolling.So the steel sheet of preparation constitutes simulated panel shown in Figure 7, and applies 2,4,8% strain, and then 170 ℃ of thermal treatments 20 minutes, described thermal treatment is equivalent to coating-baking processing.Table 6 expression panel anti-rabbing property (strains of 2,4,8% 3 levels) and panel apply the evaluation result of 2% strained shape stability.Sample No.4-7, the 9-12,15-18,20,21,27-29,32-34 and the 36-39 that are shown in table 6 are within the scope of the invention.On the other hand, No.1-3,8,13,14,19,22-26,30,31,35 and 40 expression Comparative Examples.

The finishing temperature of each in Comparative Examples No.1～3 and the 23-26 steel sample is lower than (Ar ₃-100) ℃, not within the scope of the invention.In the steel sample of these Comparative Examples each shows the 2%P0.1-8%P0.1 value for 140N-158N and 140N-165N as a result, the Wca value is respectively 0.38 μ m～0.43 μ m and 0.37 μ m～0.59 μ m, and the result can not obtain good panel anti-rabbing property and outstanding shape stability.The coiling temperature of each in Comparative Examples No.8,14,31 and 35 steel samples is lower than 500 ℃, and the high anti-rabbing property that shows in these steel samples is that the 2%-8%P0.1 value is 160N-189N.Yet these steel samples Wca is up to 0.23-0.45 μ m, and springback capacity δ is 7-8%, shows that their panel shape stability is poor.

In addition, the coiling temperature of each in Comparative Examples No13,19,22,30 and 40 steel samples is higher than 700 ℃.It is that the 2%-8%P0.1 value is 145N-166N that in these steel samples each shows low anti-rabbing property.And its Wca is 0.33～0.42 μ m, shows that the shape stability of panel is poor.

On the other hand, each among steel sample No.4-7,9-12,15-18,20,21,27-29,32-34 and the 36-39 is aspect finishing temperature and the coiling temperature all in the scope in the present invention regulation.Found that its 2%-8%P0.1 value is 153N-188N, shows to have good panel anti-rabbing property.Sample of the present invention also satisfies the requirement of δ value, i.e. δ≤5%, and to satisfy that Wca requires be Wca＜0.2 μ m, shows to have good shape stability.

Table 6

The condition numbering	The steel sample numbering	Finishing temperature (℃)	Coiling temperature (℃)	????σ0.2 ????(MPa)	σ(ε＝0.02) ????(MPa)	??σ(ε＝0.04) ????(MPa)
							????1 ????2 ????3 ????4 ????5 ????6 ????7 ????8 ????9 ????10 ????11 ????12 ????13 ????14 ????15 ????16 ????17 ????18 ????19 ????20 ????21 ????22	Steel 2	????780 *	????550 ????600 ????660	????215 ????218 ????217	????283 *????284 *????282 *	????313 *????315 *????318 *
????820	????530 ????590 ????630 ????680	????230 ????230 ????235 ????233	????294 ????291 ????294 ????294	????325 ????325 ????328 ????326
					????860	????460 *????550 ????600 ????640 ????680 ????730 *			????245 ????231 ????233 ????235 ????230 ????220	????299 *????295 ????294 ????296 ????294 ????285 *	????331 *????328 ????327 ????330 ????328 ????318 *
????900	????450 *????540 ????600 ????650 ????680 ????725 *	????249 ????235 ????232 ????235 ????230 ????217	????303 *????298 ????296 ????299 ????295 ????283 *	????337 *????330 ????328 ????330 ????330 ????316 *
					????930	????550 ????680 ????750 *			????235 ????233 ????220	????295 ????295 ????285 *	????331 ????330 ????318 *

(continuing)

Table 6

The condition numbering	??σ(ε＝0.08) ????(MPa)	2％，4％，8％P0.1 ????(N)	????δ ????(％)	????Wca ????(μm)	Remarks
						????1 ????2 ????3 ????4 ????5 ????6 ????7 ????8 ????9 ????10 ????11 ????12 ????13 ????14 ????15 ????16 ????17 ????18 ????19 ????20 ????21 ????22	????379 *????384 *????381 *	????140-155 ????144-155 ????144-158	3(○) 2(○) 5(○)	0.38(△) 0.4(△) 0.43(×)	Comparative Examples Comparative Examples Comparative Examples
????390 ????387 ????394 ????391	????155-177 ????153-175 ????155-177 ????155-178	4(○) 4(○) 4(○) 5(○)	0.12(○) 0.1(○) 0.18(○) 0.16(○)	The present invention of the present invention
					????390 *????392 ????392 ????394 ????391 ????388 *		????160-176 ????158-179 ????157-179 ????158-177 ????156-178 ????148-162	7(△) 5(○) 4(○) 5(○) 5(○?) 3(○)	0.23(△) 0.14(○) 0.15(○) 0.08(○) 0.18(○) 0.36(△)	Comparative Examples Comparative Examples of the present invention
????397 *????395 ????390 ????393 ????393 ????385 *	????161-181 ????158-178 ????157-177 ????159-179 ????158-179 ????146-166	8(△) 4(○) 4(○) 5(○) 5(○) 3(○)	0.26(△) 0.18(○) 0.12(○) 0.1(○) 0.12(○) 0.42(×)	Comparative Examples Comparative Examples of the present invention
					????394 ????394 ????388 *		????158-178 ????158-179 ????149-165	4(○) 5(○) 3(○)	0.15(○) 0.19(○) 0.41(×)	Comparative Examples of the present invention

Annotate: symbol ^*The expression value is not in the scope of the present invention's regulation

Table 6 (continuing)

The condition numbering	The steel sample numbering	Finishing temperature (℃)	Coiling temperature (℃)	??σ0.2 ??(MPa)	??σ(ε＝0.02) ????(MPa)	??σ(ε＝0.04) ????(MPa)
							????23 ????24 ????25 ????26 ????27 ????28 ????29 ????30 ????31 ????32 ????33 ????34 ????35 ????36 ????37 ????38 ????39 ????40	Steel 14	????750 *	????450 *????550 ????650 ????750 *	????214 ????217 ????217 ????215	????280 *????282 *????282 *????284 *	????315 *????320 *????318 *????320 *
????840	????550 ????600 ????650 ????730 *	????238 ????235 ????235 ????220	????303 ????295 ????297 ????285 *	????335 ????333 ????332 ????320 *
					????890	????440 *????550 ????650 ????680			????247 ????235 ????237 ????237	????301 *????296 ????297 ????303	????335 *????334 ????335 ????335
????920	????460 *????520 ????580 ????640 ????680 ????730 *	????250 ????236 ????233 ????235 ????231 ????219	????303 *????295 ????297 ????297 ????294 ????284 *	????339 *????333 ????332 ????335 ????331 ????318 *

(continuing)

Table 6 (continuing)

The condition numbering	??σ(ε＝0.08) ????(MPa)	??2％，4％，8％P0.1 ????(N)	??δ ??(％)	??Wca ??(μm)	Remarks
						????23 ????24 ????25 ????26 ????27 ????28 ????29 ????30 ????31 ????32 ????33 ????34 ????35 ????36 ????37 ????38 ????39 ????40	????382 *????382 *????385 *????385 *	????140-160 ????145-160 ????145-165 ????147-165	3(○) 3(○) 2(○) 2(○)	0.4(△) 0.37(△) 0.43(×) 0.59(×)	Comparative Examples Comparative Examples Comparative Examples Comparative Examples
????401 ????400 ????405 ????388 *	????160-185 ????156-183 ????157-188 ????147-165	5(○) 5(○) 4(○) 3(○)	0.18(○) 0.15(○) 0.15(○) 0.33(△)	Comparative Examples of the present invention of the present invention
					????405 *????400 ????401 ????403		????160-189 ????157-183 ????158-185 ????160-185	8(△) 5(○) 5(○) 5(○)	0.3(△) 0.19(○) 0.18(○) 0.13(○)	Comparative Examples the present invention of the present invention
????403 *????401 ????403 ????402 ????397 ????385 *	????160-187 ????156-185 ????158-187 ????157-185 ????155-181 ????145-166	7(△) 5(○) 5(○) 5(○) 5(○) 3(○)	0.45(×) 0.19(○) 0.1?9(○) 0.17(○) 0.15(○) 0.38(△)	Comparative Examples Comparative Examples of the present invention

Annotate: symbol ^*The expression value is not in the scope of the present invention's regulation

Commercial Application

As mentioned above, the present invention can the satisfied desired anti-rabbing property of steel plate, surperficial shape stability, anti-natural ageing performance and the hot strength as the automobile external panel of steady production be 340MPa or higher cold-rolled steel sheet and galvanized steel plain sheet by composition, tensile properties and the manufacturing process condition of regulation steel. Therefore, the present invention has very high value in steel and iron industry and auto industry.

Claims (7)

1. cold-rolled steel sheet with outstanding panel shape stability and anti-rabbing property, the C that contains weight percent 0.004～0.015%, the Si of weight percent 0.01～0.2%, the Mn of weight percent 0.1～1.5%, the P of weight percent 0.01～0.07%, the S of weight percent 0.005～0.015%, the solid solution attitude Al of weight percent 0.01～0.08%, weight percent is not more than 0.005% N, be selected from least a element in the group that the Ti by the Nb of weight percent 0.02～0.12% and weight percent 0.03～0.1% forms in addition, and the Fe of equal amount and unavoidable impurities, C wherein, Nb, Ti, N and S satisfy the relation of formula (1) expression, and cold-rolled steel sheet satisfies the relation of formula (2) expression:

-0.001≤C％-(12/93)Nb％-(12/48)Ti ^*≤0.001????…(1)

Wherein, Ti ^*=Ti%-(48/14) N%-(48/32) S% works as Ti ^*Be not more than at 0 o'clock, think Ti ^*Be 0;

exp(ε)×(5.29×exp(ε)-4.19)≤σ/σ _0.2≤exp(ε)×(5.64×exp(ε)-4.49)????????????????????????????????????…(2)

0.002＜ε≤0.096 wherein, ε represents true strain, σ _0.2Represent 0.2% proof stress, σ represents the true stress with respect to true strain ε.

2. cold-rolled steel sheet as claimed in claim 1 is characterized in that, also comprises the B of weight percent 0.0001～0.002%.

3. cold-rolled steel sheet as claimed in claim 1 or 2 is characterized in that, is coated with zinc above the described cold-rolled steel sheet.

4. a method of making cold-rolled steel sheet as claimed in claim 1 or 2 comprises the following steps:

At first prepare the described steel of molten steel and continuous casting; Carry out hot rolling then, wherein at (Ar ₃-100) ℃ or higher temperature carry out finish to gauge to form hot rolled strip; And batch described steel band at 500～700 ℃;

Hot rolled strip is carried out cold-rolling treatment continuously.

5. method as claimed in claim 4 also comprises the following steps:

Hot rolled strip is carried out anneal and zinc-plated processing.

6. method as claimed in claim 4 also comprises the following steps:

Described hot rolled strip is carried out anneal.

7. method as claimed in claim 4 also comprises the following steps: hot rolled strip is carried out zinc-plated processing.

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