CN100439544C - High-strength cold-rolled steel sheet and manufacturing method thereof - Google Patents

Abstract

The invention relates to a high-strength cold-rolled steel plate, which contains C: less than 0.015%, Si: less than 1.5%, Mn: 0.4-3%, P: less than 0.15%, S: less than 0.02%, and sol. Al: 0.1 to 1%, N: 0.01% or less, Ti: 0.2% or less, the balance Fe and unavoidable impurities, and satisfy 1≤([Ti]/48)/([C]/12+[N] /14), wherein, [M] represents the content of the element M. The high-strength cold-rolled steel sheet of the present invention has a TS of 340 to 590 MPa and has excellent deep drawing formability, so it is suitable for difficult-to-form automobile parts such as side outer panels and door inner panels.

Description

High-strength cold-rolled steel sheet and manufacturing method thereof

technical field

The present invention relates to a high-strength cold-rolled steel sheet used in automobiles and home appliances, in particular to a high-strength cold-rolled steel sheet with a tensile strength TS of 340-590 MPa and excellent deep drawing formability and a manufacturing method thereof.

Background technique

Conventionally, IF (Interstitial Free) soft cold-rolled steel sheets (SPC270E) with a TS of about 270 MPa and an r value of 1.8 to 2.0, which have excellent deep draw formability, have been used for difficult-to-form automotive parts such as side outer panels and door inner panels. , F). In recent years, the demand for lightweight automobile bodies has become higher and higher. For these difficult-to-form parts, IF high-strength cold-rolled steel sheets with a TS of 340-590 MPa have also begun to be applied. However, if the current mass-produced high-strength cold-rolled steel sheets with TS of 340-390 MPa and r value of about 1.7, high-strength cold-rolled steel sheets with TS of about 440 MPa and r value of about 1.5, and TS of about 590 MPa, r High-strength cold-rolled steel sheets with a value of about 1.0 are used to form these parts, and cracks are prone to appear in the stamping parts. Therefore, in fact, any high-strength cold-rolled steel sheets are only suitable for relatively shallow stamping parts. Therefore, there is a need for high-strength cold-rolled steel sheets with a TS of 340-590 MPa and a relatively high r value. Specifically, when TS is 340 to 400 MPa, it has an r value of 1.8 or more; when TS is 400 to 590 MPa, it has an r value of 1.6 or more, preferably 1.7 or more.

So far, as a method to increase the r value, use IF steel that reduces C and N as much as possible and adds a large amount of Ti and Nb. Coarsening and methods for promoting the formation and growth of recrystallized grains having a texture favorable to the r value during annealing are known. In the same way, in Japanese Patent Application Publication No. 6-108155 and Japanese Patent No. 3291639, a kind of IF steel that uses Ti as much as possible to reduce C and N and adds Ti is disclosed to generate Ti (C, S), which is beneficial to annealing. Ensembles of r-values combine reinforcement methods.

However, in the method disclosed in JP-A-6-108155, if a soft cold-rolled steel sheet having a TS of 260 to 300 MPa is applied, a large amount of conventional P and Mn is applied, and the IF having a TS of 340 MPa or more is high. In the case of cold-rolled steel sheets, a large amount of P compounds such as Fe-Ti-P and Fe-Nb-P are formed at the grain boundaries during coiling after hot rolling, so the r value is significantly lowered due to the large amount of Mn itself. In addition, in the method disclosed in Japanese Patent No. 3291639, a high-strength cold-rolled steel sheet for deep drawing with a TS of 340 MPa or more is proposed by adding a large amount of P. However, there is a non-uniform structure in the thickness direction caused by P casting segregation during stamping. conditions that lead to cracks.

On the other hand, a method of improving the r value by making efforts in the casting method has also been proposed. For example, JP-A-7-188776 discloses a method of performing finish rolling while lubricating the α region during hot rolling. Japanese Unexamined Patent Publication No. 9-279249 discloses a method of applying 1 to 50% rolling in the temperature range of 550 to 750° C. during annealing. In Japanese Patent Laid-Open Publication No. 2001-131643, a control of Si, Mn, and P content of Nb and B-added steel is disclosed, after pickling, cold rolling, and annealing, 0.3 to 5% of rolling is applied, and pickling is performed again. The method of making it through the hot-dip galvanizing line.

However, each of these methods requires a special manufacturing process, leading to an increase in manufacturing cost and a decrease in productivity. That is, in the method of JP-A-7-188776, it is necessary to perform recrystallization annealing of the hot-rolled steel sheet after finishing rolling in the α region. In the method disclosed in JP-A-9-279249, high-temperature-resistant rolling equipment is required in the annealing furnace. In the method disclosed in JP-A-2001-131643, pickling, annealing, and temper rolling need to be carried out twice respectively.

Contents of the invention

The object of the present invention is to provide a high-strength cold steel that does not require a special manufacturing process. When the TS is 340-400 MPa, the r value is 1.8 or more; when the TS is 400-590 MPa, the r value is 1.6 or more, preferably 1.7 or more. Rolled steel sheet and method of manufacturing the same.

Its purpose is to contain C: 0.015% or less, Si: 1.5% or less, Mn: 0.4 to 3%, P: 0.15% or less, S: 0.02% or less, sol.Al: 0.1 to 1% by mass %, N: 0.01% or less, Ti: 0.2% or less, the balance Fe and unavoidable impurities, and a high-strength cold-rolled steel sheet satisfying the following formula (1).

1≤([Ti]/48)/([C]/12+[N]/14)… (1)

However, [M] represents the content (% by mass) of the element M.

In addition, the high-strength cold-rolled steel sheet can be manufactured _by a manufacturing method comprising: heating the steel slab having the above-mentioned composition to 1080-1350° C.; Transformation point -20) ~ (Ar ₃ transformation point + 150) ° C at the finishing temperature of hot rolling, the process of making hot-rolled steel sheet; the hot-rolled steel sheet satisfies the following (5) at the coiling temperature CT The process of coiling; the process of cold-rolling the coiled hot-rolled steel plate at a rolling rate of 50-90% to obtain a cold-rolled steel plate; and continuously annealing the cold-rolled steel plate at 750-870°C , or at 600 ~ 750 ° C box annealing process.

480≤CT≤580+0.17/{([Ti]+0.08×[sol.Al])×[P]}… (5)

However, [M] represents the content (% by mass) of the element M.

Description of drawings

FIG. 1 is a graph showing the relationship between the amount of sol.Al, the r value, and TS.

FIG. 2 is a graph showing the relationship between [Si]+10×[P] and r value.

Detailed ways

The present inventors studied the influence of various alloy elements on the r-value of IF high-strength cold-rolled steel sheets, and obtained the following results.

i) Compared with the conventional high-strength cold-rolled steel sheet, the r value is significantly improved by adding a larger amount of sol.Al. In particular, this effect becomes more remarkable when 0.4% or more of Mn is added.

ii) Adding Si and P helps to increase the r value.

iii) By appropriately adjusting the amount of P, sol.Al, Ti, and Nb added if necessary, and the coiling temperature after hot rolling, a high r value can be obtained.

The present invention has been accomplished based on such results, and will be described in detail below.

1) sol.Al amount and r value

In order to study the relationship between the amount of sol.Al and the r value, the following experiments were performed.

Make C: 0.002%, Si: 0.25%, P: 0.08%, S: 0.007%, Nb: 0.015%, Ti: 0.03%, N: 0.002%, B: 0.001% as constant, the amount of sol.Al is at 0.01 A steel slab whose Mn content varies from 0.6 to 1.8% and varies from 0.6 to 1.8% is heated to 1250°C and then hot-rolled to make a hot-rolled steel sheet with a thickness of 3 mm, and a simulation is performed at 580°C for 1 hour Coil heat treatment. The hot-rolled steel sheet was cold-rolled to have a thickness of 0.75 mm, continuous annealing was performed at 820° C. for 60 seconds, and temper rolling was performed with an elongation of 0.7%. The r value and TS were measured by the following methods.

Take the JIS No. 5 test piece from the rolling direction, the direction at 45° to the rolling direction, and the direction at 90° to the rolling direction, measure the r value and TS with respect to each direction, and obtain the average value in the steel plate surface expressed by the following formula value.

Average value = ([T ₀ ]+2[T ₄₅ ]+[T ₉₀ ])/4

Among them, [T ₀ ] is the r value or TS value in the rolling direction, [T ₄₅ ] is the r value or TS value in the direction of 45° relative to the rolling direction, [T ₉₀ ] is the direction of 90° relative to the rolling direction r value or TS value.

FIG. 1 shows the relationship between the amount of sol.Al, the r value, and TS. In the graph, black dots represent the results when the amount of Mn is 1.8%, and white dots represent the results when the total amount of sol.Al and Mn is 1.8%.

When the amount of Mn is 1.8%, if the sol.Al is above 0.1%, the r value is above 1.6; if the sol.Al is 0.2-0.7%, the r value is above 1.7; if the sol.Al exceeds 0.7%, the r value decreases. If sol.Al is above 0.1%, TS exceeds 460MPa, and monotonously increases with the amount of sol.Al.

At this time, the amount of increase in TS per 1% of the amount of sol.Al was 35 MPa. Since its solid solution strengthening ability is approximately the same as that of Mn, if the total amount of sol.Al and Mn is 1.8%, the relationship between TS and r value when the strength is kept constant can be obtained as shown by the white dot. It can be seen that by adding sol.Al and reducing Mn, a higher r value can be obtained with the same strength.

In addition, if sol.Al exceeds 1%, fine AlN precipitates to the austenite grain boundaries during continuous casting of the slab, embrittles the grain boundaries, and the bending correction of the slab and subsequent rough rolling , cracks are prone to occur on the surface of the slab. Due to the cracks on the surface of the slab, it is easy to produce rusty surface defects, which significantly reduces the surface quality of the final product.

From the above results, even if TS exceeds 400 MPa, if the amount of sol. Al is 0.1 to 1%, preferably 0.2 to 0.7%, a high r value of 1.6 or more, preferably 1.7 or more can be obtained.

The reason why a high r value can be obtained when the amount of sol.Al is 0.1 to 1% is as follows. That is, since Al is an element that raises the transformation point _Ar3 , during hot rolling, after austenite is transformed into ferrite, the precipitation of carbides is promoted in the high-temperature α region, so that solid solution C is reduced, and Coarse the carbides, thus forming a recrystallized aggregate structure that is beneficial to the r value during annealing, increasing the r value. In addition, changes in the cold-rolled structure due to Al also contribute to the improvement of the r value.

2) Si, P amount and r value

In order to study the relationship between the amount of Si and P and the r value, C: 0.002%, Mn: 1%, S: 0.007%, sol.Al: 0.25%, Nb: 0.02%, Ti: 0.01%, N: 0.002% , B: 0.001% is constant, the amount of Si is varied between 0.005% and 1.5%, and the amount of P is varied between 0.003% and 0.15%, and the same experiment as in the case of 1) is carried out.

The relationship between [Si]+10×[P] and the r value is shown in FIG. 2 . The numbers in the figure indicate the amount of Si.

It can be seen that in the steel of the present invention having a sol.Al amount of 0.25%, a high r value of 1.7 or more can be obtained if the following formula (2) is satisfied.

0.3≤[Si]+10×[P]≤1.4... (2)

However, [M] represents the content (% by mass) of the element M.

However, if the amounts of Si and 10×P both exceed 1.5%, the r value will deteriorate, so the amounts of Si and P are set to be 1.5% or less and 0.15% or less, respectively.

Furthermore, when galvannealing is applied to the high-strength cold-rolled steel sheet of the present invention, since elements tend to cause poor coating adhesion, it is preferable to make the amount of Si 0.5% or less and the amount of P 0.08% or less. In addition, since Si and P are elements that contribute to solid-solution strengthening of ferrite, it is preferable that the amount of Si is 0.003% or more and the amount of P is 0.01% or more.

3) Other ingredients

C: C combines with Ti or Nb to form carbides. If the amount exceeds 0.015%, the amount of carbides will increase and the r value will decrease significantly. Therefore, the amount of C is preferably 0.015% or less, preferably 0.008% or less, and more preferably less than 0.004%. Furthermore, C also has the effect of increasing the strength by precipitation strengthening in the form of TiC and NbC. Therefore, for example, in steel having a TS of about 440 MPa, it is effective to contain 0.004% or more. That is, if the amount of C is 0.004 to 0.008%, and Ti and Nb are added so that the atomic ratio of them to C is 1.0 or more, the decrease in the r value can be suppressed and the strength can be improved. If the amount of C is less than 0.0005%, the ferrite grains will be coarsened during annealing and surface roughness will easily occur during press forming, so the amount of C is preferably 0.0005% or more.

Mn: Mn is an element that increases strength by solid solution strengthening, and is an indispensable element for IF high-strength cold-rolled steel sheets. In order to obtain a TS of 340 MPa or more, the amount of Mn needs to be 0.4% or more. On the other hand, if the amount exceeds 3%, the r value will be significantly lowered, so the amount of Mn is 3% or less, preferably 2% or less, more preferably 1.5% or less.

The reason why the r value decreases as the amount of Mn increases is not necessarily clear, but it is considered that the r value decreases because Mn interacts with solid solution C. Moreover, since Mn lowers the Ar ₃ transformation point, it makes the carbides precipitated during hot rolling finer, or delays the precipitation of carbides to increase the solid solution C, so it does not form recrystallization that is beneficial to the r value during annealing organization, and the r-value decreases.

S: S exists in steel as a sulfide. Since the ductility will deteriorate if the amount exceeds 0.02%, the amount of S is made 0.02% or less, preferably 0.01% or less. From the viewpoint of derusting properties, the amount of S is preferably 0.004% or more.

N: If the amount of N exceeds 0.01%, fine AlN, NbN, and Nb (C, N) precipitate at the austenite grain boundaries during continuous casting of slabs, embrittlement of the grain boundaries, and during slab casting, And during the subsequent rough rolling, cracks are likely to occur on the surface of the slab. Therefore, the amount of N is kept at 0.01% or less. Although it is preferable that the amount of N is as small as possible, in the existing steelmaking technology, about 0.001% is the limit.

Ti: Ti has the effect of refining the crystal grains after hot rolling, or forming precipitates with C or N, reducing solid solution C and N, and increasing the r value. In order to sufficiently exert such an effect of Ti, it is necessary to add Ti to satisfy the following formula (1).

1≤([Ti]/48)/([C]/12+[N]/14)… (1)

However, [M] represents the content (% by mass) of the element M.

However, since the r value rises very little even if the amount of Ti exceeds 0.2%, the amount of Ti is kept at 0.2% or less. When galvannealing is performed on the high-strength cold-rolled steel sheet of the present invention, it is preferable that the amount of Ti is 0.04% or less from the viewpoint of preventing coating unevenness. In addition, in order to securely obtain a high r value by adding Ti, the amount of Ti is preferably 0.005% or more.

The balance is Fe and unavoidable impurities.

In addition to the above components, it is preferable to add 0.002% or more of Nb to obtain a higher r value. In this case, it is necessary to adjust the amounts of Nb, Ti, C, and N to satisfy the following formula (3).

1≤([Nb]/93+[Ti]/48)/([C]/12+[N]/14)… (3)

However, [M] represents the content (% by mass) of the element M.

However, if the Nb content exceeds 0.02%, fine NbN and Nb (C, N) will precipitate at the austenite grain boundaries during continuous casting of slabs, embrittlement of the grain boundaries, and during slab casting, and other During the final rough rolling, cracks are likely to occur on the surface of the slab. Therefore, the amount of Nb is kept at 0.02% or less.

Furthermore, when 0.0001% or more of B is added, the secondary working embrittlement resistance improves. However, if the amount of B exceeds 0.003%, the effect of improving the resistance to secondary working embrittlement becomes small, conversely leading to a decrease in the r value and an increase in the rolling load. Therefore, the amount of B is 0.003% or less.

In addition, in order to further increase the strength, improve the resistance to secondary processing brittleness, and increase the r value, Cu: 0.03-0.5%, Ni: 0.03-0.5%, Cr: 0.03-0.5%, Mo: 0.05-0.3%, V: Choose to add at least one element in 0.005-0.5%. At this time, since Cu and Cr degrade the surface quality, their amounts are made 0.5% or less. Since the addition of Ni will greatly increase the cost, the amount is kept at 0.5% or less. Although Mo has little adverse effect on the secondary working brittleness resistance and contributes to the improvement of the strength, it increases the yield point and deteriorates the surface accuracy of the stamped parts, so the amount is kept at 0.3% or less. V also has little adverse effect on the secondary working brittleness resistance and contributes to the improvement of the strength, but if it exceeds 0.5%, the cost will be greatly increased, so the amount is kept at 0.5% or less. When adding Cu, it is preferable to contain Ni and Cu equivalent.

In order to improve the galvanized appearance, galvanized adhesion, fatigue characteristics, toughness of the stamped part during stamping, etc., at least one element selected from Sb: 0.002-0.2%, Sn: 0.002-0.2%, and satisfy the following The above formula (4) is very effective.

0.002≤[Sb]+[Sn]/2≤0.2... (4)

However, [M] represents the content (% by mass) of the element M.

By adding Sb and Sn, it is possible to prevent surface nitriding and nitriding of the surface layer during annealing in the box annealing furnace (BAF), continuous annealing line (CAL), continuous hot-dip galvanizing line (CGL), etc. Oxidation can improve uneven coating and poor adhesion. In addition, it is possible to prevent the adhesion of zinc oxide in the zinc bath and improve the plating appearance. Furthermore, Sb and Sn can reduce surface oxidation and suppress deterioration of fatigue characteristics and deterioration of toughness after press forming.

However, if the amounts of both Sb and Sn exceed 0.2%, the adhesion and toughness of galvanizing will be deteriorated.

4) Manufacturing method

The high-strength cold-rolled steel sheet of _the present invention is manufactured by a manufacturing method, which includes: heating the steel slab having the above composition to 1080-1350°C; Point -20) ~ (Ar ₃ transformation point + 150) ° C at the finishing temperature of hot rolling to obtain a hot-rolled steel sheet; in the case of no addition of Nb, the hot-rolled steel sheet satisfies the following (5 ) under the coiling temperature CT of the formula, and in the case of adding Nb, the process of coiling the hot-rolled steel sheet at the coiling temperature CT satisfying the following formula (6); The process of cold-rolling the hot-rolled steel plate after coiling to obtain a cold-rolled steel plate; and the process of continuously annealing the cold-rolled steel plate at 750-870°C, or performing box annealing at 600-750°C .

480≤CT≤580+0.17/{([Ti]+0.08×[sol.Al])×[P]}… (5)

480≤CT≤580+0.17/{(0.6×[Nb]+[Ti]+0.08×[sol.Al])×[P]}

... (6)

However, [M] represents the content (% by mass) of the element M.

In the steel slab, the heating temperature SRT before hot rolling needs to be 1080°C or higher in order to sufficiently dissolve the P compounds of Fe-Ti-P and Fe-Nb-P formed in the slab. However, if it exceeds 1350°C, the surface quality will deteriorate, so it is necessary to make SRT 1350°C or lower.

In order to obtain an excellent appearance, it is preferable to sufficiently remove not only primary scale but also secondary scale formed during hot rolling. Heating can also be performed by a strip heater during hot rolling.

In order to refine the microstructure after hot rolling, the finishing temperature FDT of hot rolling needs to be (Ar ₃ transformation point-20) to (Ar ₃ transformation point+150)°C.

The coiling temperature after hot rolling greatly affects the r value of the cold-rolled steel sheet of the present invention to which Al, P, Ti, and optionally Nb are added. This is because P compounds of Fe-Ti-P and Fe-Nb-P, which are detrimental to the above-mentioned r value, tend to be generated in IF steel to which P is added. Generally, when the coiling temperature is set to a high temperature, the precipitates are coarsened, and the solid-solution C is reduced, the r value is significantly increased. However, if the coiling temperature is made higher than the appropriate temperature, the above-mentioned p-compounds will be formed and the r value will be significantly lowered.

Therefore, for various steels with Al, P, Ti, and Nb added as needed, the most appropriate temperature was studied. As a result, it was found that if the coiling temperature CT was not added with Nb, if it exceeded 580+0.17/ {([Ti]+0.08×[sol.Al])×[P]}, in the case of adding Nb, if it exceeds 580+0.17/{(0.6×[Nb]+[Ti]+0.08×[sol. Al])×[P]}, P compounds are generated, and the r value is significantly reduced. In addition, if the coiling temperature is lower than 480° C., even if P compounds are not formed, the precipitation of carbides during coiling is insufficient, and the r value deteriorates. Therefore, the coiling temperature CT needs to satisfy the above formula (5) or formula (6).

Coiling is preferably performed within the temperature range of (upper limit -40) to (upper limit) °C in the above formulas (5) and (6).

In cold rolling, from the viewpoint of increasing the r value, the rolling ratio needs to be 50 to 90%, preferably 65 to 80%.

The annealing temperature AT needs to be 750 to 870°C when CAL or CGL performs continuous annealing. At a temperature lower than 750°C, recrystallization is insufficient, and a high r value cannot be stably obtained. In addition, properties such as stretchability are also remarkably deteriorated. At a temperature exceeding 870°C, the steel plate containing a large amount of Mn is annealed beyond the Ar ₃ transformation point, the strength is greatly increased, and the tensile property and r value are significantly deteriorated. In order to stably obtain a high r value and high stretchability, it is preferable to perform annealing at a temperature of 820° C. or higher. In addition, when BAF is annealed, since the annealing time is long, it is necessary to set the annealing temperature AT to 600 to 750°C.

The cold-rolled steel sheet after annealing may be plated with zinc by electroplating or hot-dip plating as needed. Examples of zinc-containing plating include zinc plating, zinc alloy plating, zinc-nickel alloy plating, and the like. In addition, organic film treatment may be performed after plating.

Example

Steel Nos. A to X shown in Table 1 were produced and then continuously cast into slabs with a thickness of 230 mm. The slabs were reheated at the heating temperature SRT shown in Table 2, hot-rolled to 3.2 mm at the finishing temperature FDT shown in Table 2, and coiled at the coiling temperature CT shown in Table 2. After cold-rolling the hot-rolled sheet to a thickness of 0.8 mm, it was annealed by CAL, CGL, and BAF at the annealing temperature AT shown in Table 2, and subjected to skin pass rolling with an elongation of 0.8%, to produce steel sheets No. 1- 34. In CGL, the annealed steel sheet is dipped in a molten zinc plating bath at 460°C, and then alloyed at 500°C in a series alloying furnace. The plating basis weight was 45 g/m ² per side.

The r value and TS value were measured by the above method. In addition, surface quality was investigated by visual inspection of surface defects.

The results are shown in Table 2.

In Table 1 and Table 2, [Nb] in the uppermost formula is 0 when Nb is not added.

In steel sheets Nos. 1 to 24 which are examples of the present invention, an r value of 1.8 or more can be obtained when TS is 340 to 400 MPa, and an r value of 1.6 or more can be obtained when TS is 400 to 590 MPa, and the surface quality is also good. Furthermore, it can be seen that the r value of the example of this invention is remarkably high compared with the comparative example of the same intensity|strength. Especially when the amount of Mn exceeds 1%, the effect is more remarkable.

On the other hand, in the steel sheets Nos. 25 to 34 of the comparative examples, r values of 1.8 or more were obtained when TS was 340 to 400 MPa, and r values of 1.6 or more were obtained when TS was 400 to 590 MPa. In steel sheet Nos. 27, 28, and 29 corresponding to conventional high-strength cold-rolled steel sheets having a high Mn content, r values were low. In addition, in steel sheets No. 30, 31, 32, 33, and 34, the (Nb+Ti)/(C+N) ratio, C, Si, Mn, P, sol.Al, and Nb are outside the scope of the present invention, respectively. , low r value. Among them, the amount of C and the ratio of (Nb+Ti)/(C+N) are not appropriate, and in the steel sheet No. 30 corresponding to the conventional low-carbon high-strength steel sheet coexisting with solid solution C and Mn, even if the sol.Al is increased, High r-values cannot be obtained either. In addition, in steel sheets Nos. 31 and 34 in which Nb or Nb and sol.Al were outside the range of the present invention, the surface quality was poor.

Comparing steel sheet No. 25, which is equivalent to the conventional soft cold-rolled steel sheet SPC270F, and steel sheet No. 26 to which a large amount of sol. The effect is also small.

Table 2

※1: If the temperature exceeds 800℃, "-" will be marked.

※2: ○ means no surface defect or within the allowable range, × means scale surface defect degrades the surface.

Claims (13)

1. high strength cold rolled steel plate, in quality %, contain that C:0.015% is following, Si:1.5% following, Mn:0.4～3%, P:0.15% is following, S:0.02% is following, sol.Al:0.1～1%, N:0.01% is following, Ti:0.2% following, surplus Fe and unavoidable impurities, and satisfy following (1) formula

1≤([Ti]/48)/([C]/12+[N]/14)…(1)

Wherein, the mass percentage content of [M] expression element M.

2. high strength cold rolled steel plate as claimed in claim 1 wherein, contains sol.Al:0.2～0.7% in quality %.

3. high strength cold rolled steel plate as claimed in claim 1 wherein, satisfies following (2) formula,

0.3≤[Si]+10×[P]≤1.4…(2)

Wherein, the mass percentage content of [M] expression element M.

4. high strength cold rolled steel plate as claimed in claim 2 wherein, satisfies following (2) formula,

0.3≤[Si]+10×[P]≤1.4…(2)

Wherein, the mass percentage content of [M] expression element M.

5. high strength cold rolled steel plate as claimed in claim 1 wherein, in quality %, also contains Nb:0.002～0.02%, and satisfies following (3) formula,

1≤([Nb]/93+[Ti]/48)/([C]/12+[N]/14)…(3)

Wherein, the mass percentage content of [M] expression element M.

6. high strength cold rolled steel plate as claimed in claim 4 wherein, in quality %, also contains Nb:0.002～0.02%, and satisfies following (3) formula,

1≤([Nb]/93+[Ti]/48)/([C]/12+[N]/14)…(3)

Wherein, the mass percentage content of [M] expression element M.

7. high strength cold rolled steel plate as claimed in claim 1 wherein, in quality %, also contains B:0.0001～0.003%.

8. high strength cold rolled steel plate as claimed in claim 6 wherein, in quality %, also contains B:0.0001～0.003%.

9. high strength cold rolled steel plate as claimed in claim 1, wherein, in quality %, also contain at least a element of from Cu:0.03～0.5%, Ni:0.03～0.5%, Cr:0.03～0.5%, Mo:0.05～0.3% and V:0.005～0.5%, selecting.

10. high strength cold rolled steel plate as claimed in claim 8, wherein, in quality %, also contain at least a element of from Cu:0.03～0.5%, Ni:0.03～0.5%, Cr:0.03～0.5%, Mo:0.05～0.3% and V:0.005～0.5%, selecting.

11. high strength cold rolled steel plate as claimed in claim 1 in quality %, also contains and select at least a element from Sb:0.002～0.2% and Sn:0.002～0.2%, and satisfy following (4) formula,

0.002≤[Sb]+[Sn]/2≤0.2…(4)

Wherein, the mass percentage content of [M] expression element M.

12. high strength cold rolled steel plate as claimed in claim 10 in quality %, also contains and select at least a element from Sb:0.002～0.2% and Sn:0.002～0.2%, and satisfy following (4) formula,

0.002≤[Sb]+[Sn]/2≤0.2…(4)

Wherein, the mass percentage content of [M] expression element M.

13. the manufacture method of a high strength cold rolled steel plate comprises: will have the operation that is heated to 1080～1350 ℃ as the plate slab of the described any composition of claim 1～12;

With the plate slab after the described heating at (Ar ₃Transformation temperature-20)～(Ar ₃Transformation temperature+150) carry out hot rolling under ℃ the finishing temperature, make the operation of hot-rolled steel sheet;

Operation with described hot-rolled steel sheet batches under the coiling temperature CT that satisfies following (5) or (6) formula wherein, satisfies (5) formula when not adding Nb, satisfy (6) formula when adding Nb;

The hot-rolled steel sheet of rolling rate with 50～90% after to described batching carries out cold rolling, makes the operation of cold-rolled steel sheet; With

Under 750～870 ℃, described cold-rolled steel sheet is carried out continuous annealing, perhaps under 600～750 ℃, carries out the operation of pack annealing,

480≤CT≤580+0.17/{([Ti]+0.08×[sol.Al])×[P]}…(5)

480≤CT≤580+0.17/{(0.6×[Nb]+[Ti]+0.08×[sol.Al])×[P]}

…(6)

Wherein, the mass percentage content of [M] expression element M.

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