JP3303931B2 - High-strength steel sheet for baking having hardenability and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin steel sheet mainly used for tinplate and tin-free steel and a method for producing the same. The present invention is applied to a high-strength steel sheet for cans having heat resistance and a method for producing the same.

[0002]

2. Description of the Related Art As a conventional high-strength thin steel sheet with a surface treatment, for example, there is a method of manufacturing a thin steel sheet for a can described in Japanese Patent Application Laid-Open No. HEI 2-1-182027. In this method for producing a steel sheet for cans, a steel slab made of a so-called ultra-low carbon steel having a predetermined composition is hot-rolled and pickled by a usual method, then cold-rolled at a rolling reduction of 85 to 90%, and then subjected to continuous annealing. Apply, then the rolling reduction 15 ~
It is intended to strengthen the steel sheet by performing temper rolling in the range of 45%.

On the other hand, in order to improve the strength of a steel sheet, there has been proposed a method of producing a steel in which a solid solution strengthening element such as Si, P or the like is added as described in, for example, Japanese Patent Application Laid-Open No. 59-193221. I have.

[0004]

However, in the method for producing a thin steel sheet for a can described in Japanese Patent Application Laid-Open No. Hei 2-11802, a high strength steel sheet is obtained because the original sheet is a soft ultra-low carbon steel. In the process, secondary cold rolling with a relatively high rolling reduction after annealing is necessary, so that not only the ductility of the steel sheet is deteriorated due to the residual strain caused by rolling, but also various problems such as shape deterioration in manufacturing. There is a point. In order to solve such a problem, it is conceivable to apply a strengthening theory for ordinary steel to produce a hard original sheet by continuous annealing in a component system in which C is increased. Since the amount of solid solution C is extremely large, aging deterioration becomes remarkable, and its application is likely to be limited. In addition, since the thin steel sheet manufactured in this way has poor ductility, for example, cracks occur due to forming such as neck-in processing performed during can manufacturing, and a welded portion (Heat Affected Zone: There is a problem such as deterioration in workability of HAZ), which is a practical obstacle.

On the other hand, in the method for producing high-strength steel described in Japanese Patent Application Laid-Open No. Sho 59-193221, the problem associated with the large addition of Si, mainly the problem of surface treatment, is unavoidable. In thin steel sheets for cans used as tinplate and tin-free steel, as is known, the increase in oxidation during surface treatment increases as the Si content increases,
There is a problem that the plating layer is peeled off by prolonged heating. Further, by adding a large amount of P, problems such as deterioration of corrosion resistance and embrittlement of the material become remarkable. In addition, a significant problem is that recrystallization annealing at an extremely high temperature is required in the continuous annealing step because the recrystallization temperature of the steel sheet increases.

The present invention has been developed in view of these problems. The present invention satisfies not only press workability but also required properties such as plating property and aging deterioration resistance, and particularly has a tensile strength of 40 kgf / mm ^2. It is an object of the present invention to provide a baking-hardenable thin steel sheet for cans capable of reducing the required sheet thickness and reducing the amount of material used to reduce the cost by imparting the above high strength, and a method for producing the same. It is.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, obtained the following findings and developed the present invention. That is, in order to improve workability and aging resistance, an ultra-low carbon steel whose C content is adjusted to 0.0005% to 0.0050% is used as a material, and a large amount of Mn is added to this material, and further N is added. Thus, by providing the continuous annealing method by optimizing the hot rolling and cold rolling conditions, it is possible to achieve both an increase in strength and good workability. Further, in particular, in the case of a surface-treated steel sheet such as a steel sheet for cans, it is first required that the in-plane anisotropy of the steel sheet is small. In the present invention, this is achieved by adding a small amount of Nb. In consideration of applications where strength is further required, P and S
i is added in a limited amount. In this case, by simultaneously increasing Mn, the above-mentioned problems of these additional elements can be solved. Further, Ti, B,
Aging resistance characteristics, strength, in-plane anisotropy, plating characteristics, and the like can be improved by adding one or more of V and Ni alone or in combination.

[0008] In the present invention, the baking-hardenable high-strength steel sheet for cans according to the first aspect of the present invention has a weight ratio of C:
0.0005% or more and 0.0150% or less, Si: 0.2
0% or less, Mn: 0.50% to 2.50%, P:
0.005% or more and 0.100% or less, S: 0.010%
Below, N: 0.0030% to 0.0150%, N
b: 0.003% or more and 0.020% or less, Al: 0.0
Contains not less than 05% and not more than 0.100%, with the balance being F
e and unavoidable impurities.

[0009] In the present invention, the baking-hardenable high-strength steel sheet for cans according to claim 2 has a weight ratio of C: 0.0.
005% to 0.0150%, Si: 0.20% or less, Mn: 0.50% to 2.50%, P: 0.0
05% or more and 0.100% or less, S: 0.010% or less,
N: 0.0030% to 0.0150%, Nb:
0.003% to 0.020%, Al: 0.005
% Or more and 0.100% or less, and Ti: 0.0
0.05% or more 0.0 1 0% or less, B: 5 ppm or more 20p
pm or less, Mo: 0.010% or more and 0.300% or less,
V: 0.010% to 0.300 % , Ni: 0.0
One or more components of not less than 0.05% and not more than 0.300%, Cu: not less than 0.005% and not more than 0.300%,
The balance consists of Fe and inevitable impurities.

In the present invention, the method for producing a baking-hardenable high-strength steel sheet for a can according to the present invention comprises:
C: 0.0005% to 0.0150%, Si:
0.20% or less, Mn: 0.50% to 2.50%, P: 0.005% to 0.100%, S: 0.
010% or less, N: 0.0030% or more and 0.0150%
Nb: 0.003% to 0.020%, A
l: A steel slab containing 0.005% or more and 0.100% or less and the balance being Fe and unavoidable impurities is used as a raw material, and re-heated to a temperature range of 1150 ° C or more and 1300 ° C or less and hot-rolled. (Ar ₃ transformation point −30 ° C.)
Finish rolling in the temperature range of ~ (Ar ₃ transformation point + 100 ° C), winding it at a temperature of 450 ° C or more and 650 ° C or less, pickling, and cooling at a cold rolling reduction of 70% or more. Rolling, annealing at 700 ° C. or more and 800 ° C. or less, and then 10 ° C./sec. After rapidly cooling to a temperature of 500 ° C. or less at the above cooling rate, temper rolling of 1% or more and 40% or less is performed.

[0011] In the present invention, the method for producing a baking-hardenable high-strength steel sheet for cans according to claim 4 is:
C: 0.0005% to 0.0150%, Si:
0.20% or less, Mn: 0.50% to 2.50%, P: 0.005% to 0.100%, S: 0.
010% or less, N: 0.0030% or more and 0.0150%
Nb: 0.003% to 0.020%, A
l: 0.005% to 0.100% or less of the ingredients, Ti: 0.005% or more 0.0 1 0% or less, B: 5
ppm to 20 ppm, Mo: 0.010% to 0.300%, V: 0.010% to 0.300 %
Ni: 0.005% or more and 0.300% or less, C
u: A steel slab containing one or more components of 0.005% or more and 0.300% or less and the balance being Fe and unavoidable impurities is used as a raw material, and the temperature range is 1150 ° C or more and 1300 ° C or less. Re-heat to start hot rolling, (Ar ₃
Exit finish rolling in the temperature range of the transformation point over 30 ℃) ~ (Ar ₃ transformation point + 100 ° C.), which 450 ° C. or more on 6 5
After winding at a temperature of 0 ° C. or less, pickling, cold rolling at a cold rolling reduction of 70% or more, annealing at 700 ° C. to 800 ° C., and then 10 ° C./sec. 5 at the above cooling rate
After rapidly cooling to a temperature of 00 ° C. or less, temper rolling of 1% or more and 40% or less is performed.

[0012]

The reasons for limiting the structural requirements in the baking-hardenable steel sheet for cans according to the present invention and the method for producing the same will be described below. C: About the setting of 0.0005% or more and 0.0150% or less by weight The reduction of the amount of C added is due to the ductility expressed by El (Elongation) value and the deep drawability expressed by r value (Rankford value). Although it is desirable from the viewpoint of improvement, when the content is 0.0005% or less, there is a great risk of causing a rough surface after press working due to remarkable coarsening of the particle size, so-called orange peel phenomenon, and causing a trouble. When added in an amount exceeding 0.0150%, the r-value tends to decrease and A
The aging resistance characteristic represented by I (Aging Index) value is remarkably deteriorated. Further, as a material for a three-piece can, a welded portion (HA
The hardening of Z) becomes remarkable, and the workability of the portion is remarkably deteriorated, which is not desirable. Therefore, in the present invention, the amount of C added is set to be 0.0005% or more and 0.0150% or less by weight.

Mn: 0.50% to 2.50% by weight
Regarding the following settings: Mn must be added according to the amount of S contained in order to prevent the so-called red-hot brittleness of steel, which causes cracks near the red-hot temperature (950 ° C) during press working. However, in the present invention, it is one of the extremely important additional elements for the following reasons. First, by adding Mn, it is possible to increase the strength without remarkable deterioration of the material, possibly in connection with the lowering of the transformation point, although the detailed mechanism is still unknown. Although the solid solution strengthening ability of Mn itself does not seem to be so great, refining of the structure occurs remarkably,
Among the specification characteristics as a steel sheet for cans, the surface roughness resistance, the joint characteristics of the welded portion, and the like are significantly improved. Furthermore, the addition of Mn lowers the recrystallization temperature in the annealing step after cold rolling, and alleviates operating conditions, although the detailed mechanism is still unknown, but is presumed to be due to uniform coarsening of precipitates. The effect of being able to do so became clear. Such an effect becomes remarkable when the added amount of Mn is about 0.50% or more. However, when the added amount exceeds 2.50%, the hot-rolled base sheet is extremely hardened and cold rolling becomes extremely difficult. Therefore, in the present invention, the amount of added Mn is set to 0.50% to 2.50% by weight.

Si: about 0.200% by weight or less Si has a solid solution strengthening ability larger than other alloying elements and is an element that one wants to use as much as possible. Is remarkable, the upper limit of the addition amount is regulated.
The upper limit of the level at which there is no problem in the surface treatment properties of a surface-treated steel sheet, particularly a steel sheet for cans, is 0.200% or less. Therefore,
In the present invention, the amount of Si added is set to 0.200% or less by weight.

P: 0.005% to 0.100 by weight
% Or less P, like Si, has a large solid solution strengthening ability and is an element to be used as much as possible. However, when added in a large amount as described above, problems such as deterioration of corrosion resistance and embrittlement of the material become remarkable. Not only that, but it also increases the recrystallization temperature, so the upper limit of the amount added is restricted. The hardening caused by the addition of P appears at about 0.005% or more of the added amount, and the above-mentioned problems appear only at about 0.100%. Therefore, in the present invention, the P content is 0.005% by weight.
It is set to at least 0.100%.

S: About the setting of the weight ratio of 0.010 or less S reduces the amount of precipitates in the steel, thereby improving workability and improving the effective amount of Ti for fixing C. It is an element that you want to remove for such reasons. Such an effect can be obtained by setting the addition amount of S to 0.010% or less. However, desirably 0.005% or less is more advantageous from the viewpoint of weldability and corrosion resistance.

N: 0.0030% to 0.01 by weight
N is an element actively used in the present invention. That is, the purpose is to add a large amount of N to solid-solution strengthen steel. It has now been found that this effect is more pronounced in the component system of the present invention in which Mn is added in a relatively large amount. Such strengthening by N is naturally exerted even at room temperature, but is effective not only at a relatively high temperature range of 80 to 150 ° C. but also for improving the pressure resistance at the time of heat treatment after filling the contents of the beverage can. There is utility. Such a strengthening effect becomes remarkable when the amount of addition is approximately 0.0030% or more. When the amount exceeds 0.0150%, not only the effect tends to be saturated but also the mother plate This is not desirable because the risk of excessive hardening and the risk of defects during continuous casting of steelmaking increases. Therefore, in the present invention, the amount of N added is set to 0.0030% to 0.0150% by weight.

Nb: 0.003% to 0.02 by weight
Setting at 0% or less By adding Nb at 0.003% or more, the in-plane anisotropy of the steel sheet can be improved. Further, such a small amount of addition is effective in improving weldability. Furthermore, it is also effective at the same time for crystal grain refinement, and a small amount of addition is desirable from the viewpoint of preventing roughening of the surface during molding. But 0.020
%, The recrystallization temperature rises, and the conditions of the annealing step after cold rolling become severe. Therefore, in the present invention, the amount of Nb added is set to 0.003% or more to 0.020% by weight.
%.

[0019] · Al: Al is also Ri one der the important element component in the present invention for the weight ratio of 0.005% to 0.100% or less of the setting, the detailed mechanism but is still unknown, the amount To 0 . By setting the content to 005% or more, it is effective to maintain a good material when the winding process is performed at a low temperature during hot rolling as in the present invention. But the addition amount is not only cost over ingot exceeds 0.1 0 0% undesirable leads to rolling of degradation. Therefore, the weight ratio of 0.0 05 Al addition amount in the present invention
% To 0.100%.

The above are essential elements, and the reasons for limiting the selectively added elements will be described below. · Ti: reduction of solid solution C by adding Ti for setting a weight ratio of 0.005% or more 0.0 1 0% or less is possible, and is added effective for applications where severe aging resistance is required is there. In addition, it is as effective as Nb for refining the structure,
Generally although the effect by the addition of 0.005% or more is exhibited, excessive addition, i.e. 0.0 1 0% over the case of adding in the rapid increase of surface defects weldability occurs, even secondary resistance Problems such as deterioration of processing brittleness occur. Therefore, in the present invention, Ti
To set the amount of weight less than 0.005% 0.0 to 1 0% or less.

B: 0.0005% or more by weight 0.00
Regarding the setting of 20% or less In the present invention, it is advantageous to add B selectively from the viewpoint of the effect on secondary work brittleness, weldability and stress corrosion cracking resistance. Such an effect does not appear unless at least 0.0005% or more is added. On the other hand, if it is added in excess of 0.0020%, the in-plane anisotropy increases significantly, which leads to poor ear formation as a steel sheet for cans, which is not preferable. Therefore, in the present invention, the amount of B added is set to be 0.0005% or more and 0.0020% or less by weight.

Mo: 0.010% by weight or more and 0.30 by weight
Regarding the setting of 0% or less Mo is an advantageous additive element in that it has a large solid solution strengthening ability as a strengthening element and has little adverse effect on surface treatment properties. The strengthening effect becomes remarkable when the addition amount is approximately 0.010% or more, but when the addition amount exceeds 0.300%, not only the alloy cost increases but also recrystallization is remarkably suppressed, so that cold rolling is performed. Subsequent annealing becomes extremely difficult. Therefore,
In the present invention, the amount of Mo added is 0.010% or more by weight to 0.1%.
It was set to 300% or less.

V: 0.010% to 0.300 by weight
% Or less V is an additional element that is also useful as a strengthening element and has little adverse effect on surface treatment properties. The strengthening effect becomes remarkable at an addition amount of about 0.010% or more, while 0.300%
If the addition exceeds that, not only the alloy cost is increased but also the hot rollability is significantly deteriorated, which is not preferable. Therefore, in the present invention, the addition amount of V is 0.010% or more by weight and 0.30% or more.
It was set to 0% or less.

Ni: 0.005% to 0.30 by weight
Regarding the setting of 0% or less Ni has been conventionally not particularly added because it is an expensive element, but in the present invention, it is possible to strengthen the steel by selectively adding it. The mechanism of strengthening is thought to be due to grain refinement rather than solid solution strengthening, and it is advantageous for a steel sheet for cans from the viewpoint of preventing surface roughening resistance. Further, it has been clarified that it is also effective in suppressing various embrittlement phenomena. The improvement effect becomes apparent when the addition amount is about 0.005% or more, but tends to be saturated when it exceeds 0.300%. Therefore, in the present invention, the addition amount of Ni is set to 0.0
It was set to not less than 05% and not more than 0.300%.

Cu: 0.005% to 0.30 by weight
Regarding the setting of 0% or less Cu has not conventionally been particularly added for the same reason as that of Ni, but in the present invention, the addition amount of Cu is set to 0.005% or more by weight for the same reason as that of Ni. .30
It was set to 0% or less. Next, the reasons for limiting the manufacturing method will be described.

Slab reheating temperature: 1150 ° C. or higher 13
About the setting below 00 ° C The temperature at which the slab after continuous casting is heated prior to hot rolling is 1
Below 150 ° C., it is difficult to ensure a sufficiently high hot rolling finish temperature in hot rolling. If the rolling temperature is assured by modifying the equipment, it is advantageous in terms of material to reduce the reheating temperature. However, if the reheating temperature is reduced, the load at the time of hot rolling also increases. Therefore, the lower limit of the reheating temperature is set to 1150 ° C. on the premise of the current equipment. On the other hand, if the heating temperature exceeds 1300 ° C., the properties of the surface of the steel sheet eventually deteriorate significantly. Therefore, in the present invention, the slab reheating temperature is set to 1150 ° C. or more and 1300 ° C. or less.

Finish rolling temperature: (Ar ₃ transformation point −30)
° C.) ~ (Ar ₃ transformation point + 100 ° C.) of the finish rolling temperature for setting -30 ° C. From (Ar ₃ transformation point in order to improve the processability represented by r value after cold rolling-annealing) or more and It is necessary to. If it is less than this, the final structure tends to be coarse, which is not desirable as a steel sheet for cans from the viewpoint of skin roughness resistance. Further, when the finishing rolling temperature is lower than this, a so-called ridging phenomenon is easily caused, and the risk of pointing out a poor appearance at a user use stage increases. The upper limit temperature must be (Ar ₃ transformation point + 100 ° C.).
That is, when the finish rolling temperature is (Ar ₃ transformation point + 100 ° C.) or more, the damage of the hot rolled roll becomes large, which not only causes a great obstacle to actual production but also tends to disturb the surface properties of the steel sheet itself. This is not desirable. Not only that, the microstructure tends to be coarse, and the tensile properties of the final steel sheet deteriorate, which is also undesirable as a steel sheet for cans. Therefore, in the present invention, the finish rolling temperature is set to (Ar ₃ transformation point−30 ° C.) to (Ar ₃ transformation point + 100).
° C).

Winding temperature: about 450 ° C. or more and 650 ° C. or less If the winding temperature is less than 450 ° C., unevenness in cooling causes irregularities in the shape of the plate, which hinders pickling and cold rolling in the next step. Come. On the other hand, when the winding temperature exceeds 650 ° C., not only the pickling property deteriorates with the increase in the scale thickness generated on the steel sheet surface, but also the microstructure of the mother plate becomes coarse, so that the final strength of the steel sheet is increased. Is undesirable because it leads to a decrease in Further, when the winding temperature is 650 ° C. or higher, it is not preferable because the variation in the material in the width direction of the steel sheet becomes remarkable due to a difference in cooling rate after winding. Therefore, in the present invention, the winding temperature is set at 450 ° C. or more and 650 ° C. or less.

Cold rolling reduction: set at 70% or more If the cold rolling reduction after pickling is less than 70%, sufficient deep drawability cannot be obtained, so the lower limit is set to 70%. It is preferable that the rolling reduction is 80% or more. Therefore, in the present invention, the cold rolling reduction after pickling is set to 70% or more. -Annealing temperature: about 700 ° C or more and 800 ° C or less Annealing temperature is 700 as the minimum temperature at which recrystallization is completed.
° C is specified. On the other hand, if high-temperature annealing is performed unnecessarily, not only the risk of causing defects such as heat buckle or plate breakage during continuous annealing increases, but also the surface treatment property is deteriorated due to an increase in surface concentration. Undesirable because. The critical upper limit temperature at which such a problem does not occur is 800 ° C. Therefore, in the present invention, the annealing temperature is set to 700
The temperature was set to not lower than 800 ° C and not lower than 800 ° C.

Cooling: 10 ° C./sec. At a cooling rate of 5
Setting for rapid cooling to a region of not more than 00 ° C. When the cooling rate from the annealing temperature is not more than 10 ° C., not only the strength is reduced, which is not desirable, but also the secondary work brittleness is deteriorated. Unless the temperature is rapidly cooled to 500 ° C. or less, it is not preferable in terms of strength and brittleness in secondary processing. Therefore, in the present invention, the cooling step is performed at 10 ° C./sec. At a cooling rate of 500 ° C. or less.

Temper rolling reduction after annealing: Setting of 1% or more and 40% or less When the base plate is annealed, the yield point elongation is present and the material is not stable. Is 1%
It is necessary to perform the above temper rolling. Further, when rolling is performed at more than 40%, the steel sheet hardens and cold rolling becomes difficult, and in addition, disorder of the shape becomes apparent, which is not desirable. Further, the ratio of reinforcement tends to be saturated by processing. Therefore, in the present invention, the temper rolling reduction after annealing is set to 1% or more and 40% or less.

According to the baking-hardenable high-strength steel sheet for cans and the method for producing the same which satisfies the above conditions, the steel sheet for high-strength cans having a tensile strength of about 40 kgf / mm ² or more can be stabilized. Can be provided.

[0033]

Embodiment 1 Next, an embodiment of the present invention will be described. First, the composition shown in Table 1 below was included, and the balance was substantially F
The steel made of e was melted by an actual converter, and the steel slab was reheated to 1250 ° C. within the range set in the present invention, and finish rolling was completed in the temperature range of 860 to 950 ° C. set. At this time, the finish rolling temperature is set according to the present invention in accordance with each steel composition (Ar ₃ transformation point −30 ° C.) to (Ar
₍₃ transformation point + 100 ° C).
This hot-rolled steel sheet is wound at a winding temperature of 600 ° C. within the range set by the present invention, pickled, and then cold rolled at a rolling reduction of 86% within the range set by the present invention. 0.30
mm cold-rolled steel sheet. In Table 1, the underlined composition weight ratios are out of the range of the present invention.

[0034]

[Table 1]

The thin steel sheet thus obtained is heated in a continuous annealing furnace to 750 ° C. which is within the set range of the present invention.
Annealing is carried out by soaking for 20 sec., Then quenched to 350 ° C. at a cooling rate of 25 ° C./sec. Which is within the set range of the present invention, and then temper rolling at a rolling reduction shown in Table 2 below. went. Then, tin plating corresponding to No. 25 was continuously applied on a halogen type electric tin plating line to finish the tinplate. The thin steel sheet for cans obtained in this manner was subjected to Rockwell hardness, Tensile Strength (TS),
Average r value, Δr value, bake hardness (Baked Hardness: B
Table 2 below shows the results of the investigation for H). In addition, the tensile property was implemented using the normal JIS No. 5 test piece. Further, the steel plate was made into a two-piece can having a size of 350 cm ³ , subjected to a paint baking treatment, sampled from the body of the can, and subjected to a tensile test.

[0036]

[Table 2]

As is clear from this table, the baking-hardenable high-strength steel sheet of the embodiment of the present invention does not deteriorate in the r-value, although the desired high strength is obtained. Moreover, the Δr value is small and good. In addition, since the original plate has high bake hardenability, it can be seen that a very high strength of 70 kgf / mm ² or more is exhibited after baking and painting. Further, the surface properties, corrosion resistance, cold rolling property, etc., which are particularly problematic when used as a steel sheet for cans, do not deteriorate.

The characteristics of the sample of this example were also examined in the case where the sample of this example was tin-plated and then subjected to reflow treatment and made into a three-piece can. The same high strength as in the case of the two-piece can was obtained. It was confirmed that it could be obtained. Therefore, the baking-hardenable high-strength steel sheet for cans of the present invention can be used for both two-piece cans and three-piece cans in a similar manner, and can reduce the thickness of the steel sheet and reduce the gauge. It is possible to reduce the cost.

[0039]

Example 2 Next, steels having the composition shown in Table 3 below were melted in an actual converter, thin steel sheets were manufactured under the manufacturing conditions shown in Table 4 below, and various characteristics were obtained in the same manner as in Example 1. The results of the investigation are shown in Table 5 below. In Table 5, the ear ratio (%) was calculated by the following equation. Ear ratio = (maximum cup height-minimum cup height) / (minimum cup height) x 100 ... (1)

[0040]

[Table 3]

[0041]

[Table 4]

[0042]

[Table 5]

As is clear from these tables, the baking-hardenable high-strength steel sheet for cans of the embodiment according to the production method of the present invention has a high r-value and has good deep drawing properties.
In addition, the ear ratio is small due to the small Δr value, which can be said to be desirable characteristics. Also it has 4 kgf / mm ² approximately BH value,
This has an advantageous effect on the yield strength after can production. In general,
When the reduction ratio of the temper rolling is high, the BH value is apparently lowered, so that even in the thin steel plate for a high-strength can of the present invention, when the reduction ratio of the temper rolling is high, 1-2 kgf / mm ^2. Despite a slight decrease, B still exceeds ² kgf / mm ²
H value is held.

[0044]

As described above, according to the baking-hardenable high-strength steel sheet for cans and the method for producing the same according to the present invention, the high-strength steel sheet has a high strength of about 40 kgf / mm ² or more in terms of tensile strength. It has high press workability, plating property and aging resistance while having high bake hardenability, and surface properties, corrosion resistance and cold rollability which are particularly problematic when used as a steel sheet for cans. -It is possible to stably provide a steel sheet for a can without deteriorating the surface treatment properties and the like, whereby the required sheet thickness can be reduced, and the cost can be reduced by reducing the amount of material used.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Kato 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (56) References JP 62-7822 (JP, A) 63-4899 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00-38/60 C21D 9/46-9/48

Claims (4)

(57) [Claims] (1) C: 0.0005% or more by weight ratio
0150% or less, Si: 0.20% or less, Mn: 0.5
0% or more and 2.50% or less, P: 0.005% or more and 0.1
00% or less, S: 0.010% or less, N: 0.0030
% To 0.0150%, Nb: 0.003% to 0.020%, Al: 0.005% to 0.100
% Or less, and the balance consists of Fe and inevitable impurities. 2. C: 0.0005% or more by weight ratio.
0150% or less, Si: 0.20% or less, Mn: 0.5
0% or more and 2.50% or less, P: 0.005% or more and 0.1
00% or less, S: 0.010% or less, N: 0.0030
% To 0.0150%, Nb: 0.003% to 0.020%, Al: 0.005% to 0.100
% Or less, Ti: 0.005% to 0.0
10 % or less, B: 5 to 20 ppm, Mo:
0.010% to 0.300%, V: 0.010%
0.300 % or less, Ni: 0.005% to 0.3
High strength with bake hardenability, characterized by containing one or more components of not more than 00% and Cu: not less than 0.005% and not more than 0.300%, with the balance being Fe and unavoidable impurities. Thin steel sheet for cans. 3. C: 0.0005% or more by weight ratio.
0150% or less, Si: 0.20% or less, Mn: 0.5
0% or more and 2.50% or less, P: 0.005% or more and 0.1
00% or less, S: 0.010% or less, N: 0.0030
% To 0.0150%, Nb: 0.003% to 0.020%, Al: 0.005% to 0.100
% Or less, and the balance is made of a steel slab composed of Fe and unavoidable impurities.
Re-heating to the following temperature range to start hot rolling, (Ar
₃ Quit finish rolling in the temperature range of the transformation point over 30 ℃) ~ (Ar ₃ transformation point + 100 ° C.), which 450 ° C. or more on 6
After winding at a temperature of 50 ° C. or less, pickling, cold rolling at a cold rolling reduction of 70% or more, annealing at 700 ° C. to 800 ° C., and then 10 ° C./sec. A method for producing a bake-hardenable high-strength steel sheet for cans, wherein the steel sheet is quenched to a temperature of 500 ° C. or less at the above cooling rate and then temper-rolled to 1% to 40%. 4. C: 0.0005% or more by weight in terms of weight ratio.
0150% or less, Si: 0.20% or less, Mn: 0.5
0% or more and 2.50% or less, P: 0.005% or more and 0.1
00% or less, S: 0.010% or less, N: 0.0030
% To 0.0150%, Nb: 0.003% to 0.020%, Al: 0.005% to 0.100
% Or less, Ti: 0.005% to 0.0
10 % or less, B: 5 to 20 ppm, Mo:
0.010% to 0.300%, V: 0.010%
0.300 % or less, Ni: 0.005% to 0.3
1% or more and 1300 ° C or less, made of a steel slab containing one or two or more components of 0.005% or less and Cu: 0.005% or more and 0.300% or less, with the balance being Fe and unavoidable impurities. , And hot rolling is started, and (Ar ₃ transformation point−30 ° C.) to (Ar ₃ transformation point + 1)
(00 ° C), finish rolling is completed,
Coiling at 50 ° C. than the 6 50 ° C. below the temperature, after pickling, 7
Cold rolled at a cold rolling reduction of 0% or more, and
Anneal at 0 ° C. or less, and then at 10 ° C./sec. After rapidly cooling to a temperature of 500 ° C or less at the above cooling rate, 1%
A method for producing a bake-hardenable high-strength thin steel sheet for cans, wherein temper rolling of at least 40% or less is performed.