KR20100029132A - High-strength steel sheet for can manufacturing and process for manufacturing the sheet - Google Patents

Abstract

The invention provides a high-strength steel sheet for can manufacturing which is improved in both strength and ductility while clearing the ASTM regulations and is thus excellent in workability. A high-strength steel sheet of 0.1 to 0.5 mm in product sheet thickness (t) for can manufacturing which has a composition containing by mass C: 0.04 to 0.13%, Si: more than 0.01% to 0.03%, Mn: 0.1 to 0.6%, P: 0.02% or below, S: 0.03% or below, Al: 0.01 to 0.2%, and N: 0.001 to 0.02% with the balance consisting of Fe and unavoidable impurities and a ferrite-base ferrite-martensite composite structure, characterized by having a martensite fraction of 5 to less than 30%, satisfying the relationship wherein d is martensite grain diameter (μm) and t is product sheet thickness (mm), and exhibiting a 30T hardness of 60 or above. 1.0 < (1-EXP(-t x 3.0)) x 4/d...

Description

High strength steel sheet for steel production and manufacturing method {HIGH-STRENGTH STEEL SHEET FOR CAN MANUFACTURING AND PROCESS FOR MANUFACTURING THE SHEET}

TECHNICAL FIELD The present invention relates to a high strength steel sheet for steel production used as raw materials for food cans and beverage cans, and a method for producing the same. Here, the high strength steel sheet means a thin steel sheet having a tensile strength of 590 MPa or more.

Generally as a steel plate for steel making, the cold-rolled steel sheet whose product plate | board thickness t is 0.1-0.5 mm is used. The steel sheet for steel making can make the product sheet thickness t thinner, so that high strength is required as much as possible.

For this reason, conventionally, it was common to manufacture the high strength steel sheet for steel pipes by the double cold rolling method. This method is, for example, as disclosed in JP-A-38-8563 and JP-A-8-5039, after cold rolling the steel sheet once and then performing a second cold rolling. It is a method of manufacturing hardness to a predetermined value. In addition, a method of cold rolling a soft hot rolled sheet made of coarse particles has also been proposed.

However, the high strength steel sheet for steel pipes manufactured by these prior arts has the drawback that workability is extremely low, and molding defects are easy to produce in a piping process. In particular, in the case where the final process is cold rolling, this tendency is prominent because the product is made of cold ductile structure with low ductility. Moreover, although the method of performing strain removal annealing after cold rolling is also proposed, since a steel plate does not recrystallize, it is the same that ductility is kept low.

Therefore, these high-strength thin steel sheets for steel making can be used when the bending is mainly used and the ductility is not required very much, but they cannot be used when a large ductility is required. In addition, in recent years, since the thinning of the can material is rapidly progressing, the ductility of the steel sheet tends to gradually decrease, and there is a problem in that it cannot cope with the design change of the food can or the beverage can. In this way, both the strength and the ductility are required for the steel sheet for canning.

In addition, even in steel sheets for automobiles, both strength and ductility are required, and in this technical field, as shown in Japanese Patent Laid-Open No. 2004-285366, two-phase (DP) structure between a ferrite phase having excellent ductility and a hard precipitated phase is disclosed. By doing so, it is proposed to make ductility and strength compatible. However, unlike steel plates for automobiles, steel plates for food cans and beverage cans are strictly restricted to alloy components in view of their harmlessness to the human body. Not applicable For example, although the invention of Unexamined-Japanese-Patent No. 2004-285366 contains 1.5-3.5% Mn and refine | miniaturizes a crystal grain, in ASTM, the upper limit of Mn is prescribed | regulated as 0.6% and it becomes out of specification.

Moreover, when the product sheet thickness t is made thin in 0.1-0.5 mm, the improvement of the extending | stretching expressed in the automotive steel plate cannot be obtained. It is thought that this is because stress thickness of martensite and ferrite interface easily occurs in the ultrathin material because of the thin plate thickness. In addition, the particle size of martensite increases when an alloy component is reduced so that it may pass the regulation of ASTM. For these reasons, it was not possible to apply the DP technology of automotive steel sheets to high strength steel sheets for steel making and achieve both strength and ductility.

Accordingly, an object of the present invention is to solve the above-mentioned conventional problems and to provide a high-strength steel sheet for steel pipe excellent in workability in which both strength and ductility are achieved while passing the regulation by ASTM. In addition, the upper limit of the regulation of the alloy component of the steel plate for steelmaking by ASTM is as follows.

C: 0.13%, Mn: 0.60%, P: 0.020%, S: 0.03%, Si: 0.020%, Cu: 0.60%, Ni: 0.15%, Cr: 0.10%, Mo: 0.05%, Al: 0.20%, Others: 0.02%, except for Al-kilted steel, Si: 0.03%.

In the first invention of the present invention made to solve the above problems in the high-strength thin steel sheet for steel pipe of the product plate thickness t is 0.1 to 0.5mm,

In mass%,

C: 0.04 to 0.13%,

Si: greater than 0.01% to 0.03%,

Mn: 0.1-0.6%

P: 0.02% or less

S: 0.03% or less,

Al: 0.01-0.2%

N: 0.001 to 0.02%

And the balance has a steel composition composed of Fe and unavoidable impurities, and the steel structure is a complex structure of ferrite and martensite of a ferrite main body,

The martensite fraction is 5% or more and less than 30%,

The martensite particle diameter d (µm) and the product sheet thickness t (mm) satisfy the following formula <A>,

30T hardness is characterized by more than 60.

1.0 <(1-EXP (−t × 3.0)) × 4 / d... Expression <A>

Moreover, the 2nd invention of this invention is the high-strength steel sheet for steel pipes whose product plate | board thickness t is 0.1-0.5 mm, in mass%,

C: 0.04 to 0.13%,

Si: greater than 0.01% to 0.03%,

Mn: 0.1-0.6%,

P: 0.02% or less,

S: 0.03% or less,

Al: 0.01-0.2%,

N: 0.001-0.02%,

And a balance having a steel composition composed of Fe and unavoidable impurities, the steel composition being a composite structure of ferrite and martensite of a ferrite main body,

The martensite fraction is 5% or more and less than 30%,

The martensite particle diameter d (unit µm), the product sheet thickness t (mm) and the martensite hardness (Hv) satisfy the following formula <B>, and 30T hardness is 60 or more.

1.0 <(1-EXP (-t × 3.0)) × 2400 / Hv} / d ... Expression <B>

In addition, the 3rd invention of this invention is mass% in the steel composition of a 1st or 2nd invention,

Mo: 0.05% or less,

Ni: 0.15% or less,

Cr: 0.10% or less,

V: 0.02% or less,

B: 0.02% or less,

Nb: 0.02% or less,

Ti: 0.02% or less,

Hardenability can be improved by containing 1 type, or 2 or more types of.

Further, the fourth aspect of the present invention, the following first through and the hot finish rolling at a finish temperature of Ar ₃ or more as the invention of a manufacturing method of the tolerance high strength steel sheet according to any one of the third invention, then 750 ℃ After winding at a temperature, cold rolling is performed at a cold rolling rate of 80% or more, and in the annealing step, the temperature range is maintained at 100 ° C. from 750 ° C. to 400 ° C. after 3 minutes or less at Ar ₁ or more and 870 ° C. or less. It is characterized by cooling to 300 ° C. or less at a cooling rate of at least sec.

Further, the fifth aspect of the present invention, preferably include in the fourth invention, wherein the finishing temperature of the hot finish rolling Ar ₃ or more, less than 920 ℃, the average cooling at 850 ℃ to 600 ℃ in the cooling process after the The speed | rate is 20 degree-C / sec or more, and winding-up temperature shall be 550 degreeC or less.

According to the first to the second inventions of the present invention, since the martensite particle diameter d is controlled in correspondence with the product sheet thickness t, a high strength steel sheet for steel pipe can be obtained in which both strength and ductility are achieved while passing the regulation by ASTM. have. In addition, in the second invention, the martensite particle size d is controlled in consideration of the martensite hardness Hv together with the product plate thickness t, so that the strength and ductility can be achieved at a higher level.

Further, according to the third invention of the present invention, the hardenability can be improved by adding an alloying element that promotes precipitation of martensite, or the strength can be increased by adding an alloying element that compensates for the lack of strength. In addition, since the can is recycled and reused, the alloy component of the third aspect of the invention does not contain an element (an element that is difficult to remove) that is an obstacle in the recycling step.

Further, according to the fourth and fifth inventions of the present invention, the high-strength foil for steel pipes in which martensite particle size d is controlled as described in the first to third inventions of the present invention without repeating cold rolling twice. Steel sheet can be manufactured efficiently

According to the present invention, it is possible to provide a high-strength steel sheet for steel pipe excellent in workability while achieving both the strength and ductility while passing the regulation according to ASTM.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure summarized by plate | board thickness and martensite particle diameter about the good and bad of extending | stretching.
Fig. 2 is a diagram showing the superfine Vickers hardness and martensite particle size of martensite for good and bad stretching.

Implement the invention  Best practice for

High-strength thin steel sheet for steelmaking of the present invention is a mass%, C: 0.04 to 0.13%, Si: more than 0.01% to 0.03%, Mn: 0.1 to 0.6%, P: 0.02% or less, S: 0.03% or less, Al: Since 0.01-0.2% and N: 0.001-0.02% are contained and remainder has a steel composition which consists of Fe and an unavoidable impurity, the reason of numerical limitation of each component is demonstrated first.

C: 0.04 to 0.13%

C is made into 0.04% or more in order to ensure the intensity | strength required for a steel plate for cans. However, if it exceeds 0.13%, ASTM cannot be passed, so C is limited to the range of 0.04 to 0.13%. More preferably, it depends on the strength level of the steel sheet to be used. However, when the amount of C increases, the strength of the martensite obtained tends to increase. It is good.

Si: greater than 0.01% to 0.03%

Si is an element which increases the deformation resistance in hot rolling and cold rolling. In order to secure the strength, it is necessary to contain an amount exceeding 0.01%, more preferably 0.015% or more. The upper limit was made 0.03% which ASTM determines.

Mn: 0.1-0.6%

Mn is a useful element that increases the strength of the cold rolled steel sheet and prevents hot cracking caused by S, suppresses the increase in the strength of the hot rolled sheet, and further refines the grains, and by containing at least 0.1% or more, retaining at winding temperature or Even in the heat history of the winding temperature to the degree of slow cooling, it is easy to cause martensite transformation in a relatively short time. The upper limit was 0.60% which ASTM determines. More preferably, although Mn is a solid solution strengthening element, Mn tends to improve its strength as the amount added increases, so that it is 0.1% or more and less than 0.5% to achieve both stretching and strength. It is preferable.

P: 0.02% or less

P is an element that lowers the ductility of the steel sheet, and P tends to segregate in steel and causes embrittlement due to segregation. For this reason, P should be reduced as much as possible, and the upper limit was made into 0.02% in this invention. This upper limit is consistent with the value specified by ASTM.

S: 0.03% or less

Since S exists as an inclusion in steel and reduces ductility of a steel plate and causes corrosion resistance, it is good to reduce as much as possible, but in this invention, the upper limit is made into 0.03%. This upper limit is consistent with the value specified by ASTM.

Al: 0.01-0.2%

Al is a useful element that acts as a deoxidizer, improves the cleanliness of steel, and also has the effect of making the structure finer. In order to acquire such an effect, it is good to contain 0.01% or more. In addition, the upper limit was made into 0.2% which ASTM determines.

N: 0.001 to 0.02%

N is an element having the effect of raising the strength (yield strength and tensile strength) of the steel sheet by solid solution strengthening and strain age hardening, and in order to obtain such an effect, it is necessary to contain 0.001% or more. Moreover, when it contains exceeding 0.02%, since it will cause the slab crack and the internal defect of a steel plate, it is not good.

In the present invention, in addition to the basic steel composition, it contains one or two or more of Mo: 0.05% or less, Ni: 0.15% or less, Cr: 0.10% or less, V: 0.02% or less, B: 0.02% or less. You can. These are all components for improving the hardenability of the steel sheet and are effective for increasing the strength, but the upper limit thereof is limited as described above by ASTM. Although addition of these components is not essential, when the target intensity | strength is high, it is good to add suitably. Excess addition suppresses ferrite and leads to ductility reduction, and therefore the said range is appropriate also in the meaning.

In addition, in the present invention, one or two kinds of Nb: 0.02% or less and Ti: 0.02% or less may be contained in mass% in addition to the basic steel composition. These are all precipitation strengthening elements and are effective for increasing the strength. The upper limit of these components is also restrict | limited as mentioned above by ASTM. The components for improving the hardenability described above and the precipitation reinforcing component may be used alone or in combination.

The high strength steel sheet for steel production of this invention has the said steel composition, and product sheet thickness t is 0.1-0.5 mm. If the product sheet thickness t is less than 0.1 mm, production can be difficult in the current technology, and if the product sheet thickness t exceeds 0.5 mm, it is beyond the concept of the steel sheet, the product sheet thickness t is set to 0.1 to 0.5 mm. More preferably the product plate thickness t ranges from 0.1 to 0.3 mm.

 In the high strength steel sheet for steelmaking of the present invention, the steel structure is a composite structure of ferrite and martensite of a ferrite main body. Ferrite is an essential phase for improving the workability of a steel plate, and makes it a main phase. On the other hand, martensite is an essential phase in the present invention for increasing the strength of the steel sheet, and by making the two-phase structure of these ferrite and martensite, both ductility and strength are compatible.

In addition, the martensite fraction (area ratio of martensite to the structure) is preferably 5% or more and less than 30%. This is because when martensite is less than 5%, the strength is insufficient, whereas when martensite is more than 30%, the ferrite fraction is relatively lowered and workability is lowered.

In the high-strength steel sheet for steel production of the present invention, the martensite particle diameter d (µm) was controlled in relation to the product sheet thickness t (mm), so that the following formula <A> was satisfied in the first invention.

1.0 <(1-EXP (-t × 3.0)) × 4 / d ... Expression <A>

In Tables 2 and 3 (continued in Table 2) of Example 1 to be described later, the plate thickness is taken on the horizontal axis and the martensite particle size on the vertical axis, and the drawing is 5% or more. It is FIG. 1 which made it fail, and plotted and indicated by x, and the formula <A> which approximated the boundary of the pass rejection by the natural logarithm. That is, when the product plate thickness t approaches 0.1 mm, the upper limit of the martensite particle size d approaches 1 µm, and when the product plate thickness t approaches 0.3 mm, the upper limit of the martensite particle size d approaches 2.5 µm. Thus, the upper limit of the martensite particle size d is regulated in consideration of the product plate thickness t because the workability is lowered when the hard martensite particle size d becomes larger than the product plate thickness t.

In the second invention, the following formula <B> obtained by dividing 4 / d in formula <A> by 2400 / Hv divided by martensite particle size d (μm) is satisfied.

1.0 <(1-EXP (-t × 3.0)) × 2400 / Hv} / d ... Expression <B>

With respect to Tables 4 and 5 (continued in Table 4) of Example 2 to be described later, in the case of the product sheet thickness t (mm) = 0.22 mm, the ultra-fine Vickers hardness of martensite is taken along the horizontal axis, and the martensite particle size is taken along the longitudinal axis. Fig. 2 shows a plot of 1% or more of 5% or more as the pass and rejects 5% or less as X, and the approximate boundary of passability is approximated by natural logarithm.

Here, Hv is Martensitic ultra-microbe Vickers hardness, and a measuring method is hardness measured by making the measurement load into 10 g or less according to a structure by Shimadzu Corporation HMV-1AD, for example. If the ultrafine Vickers hardness Hv is greater than 300, the upper limit of the martensite particle size d becomes smaller than the value specified in the above formula.

30T hardness is evaluated based on 30T of JISZ2245. When 30T hardness is less than 60, when it is used in the body part of a can, since strength becomes insufficient, 60 or more are required, and the cooling rate or 300 degreeC of 100 degree-C / sec or more mentioned later It achieves by cooling to the following. Although an upper limit is not specifically determined, the upper limit of 30T hardness which can be achieved by the rapid cooling of a present state is about 90, and this is considered an upper limit. Further, more preferably, it is 65 to 85 in consideration of the balance between stretching and strength.

Below, the manufacturing method of the high strength steel sheet for steelmaking of this invention is demonstrated.

The high-strength thin steel sheet for steelmaking of the present invention is basically manufactured through a process of hot rolling, winding, cold rolling, annealing, and quenching. The hot-rolling is carried out at a low temperature, if possible, to reduce the grain size of the hot-rolled sheet, which is higher than 80%. By cold rolling at a cold rolling rate, the crystal grain size is reduced, austenite transformation occurs in the annealing process, and fine martensite is generated by appropriately controlling the quenching speed.

First, the hot rolling is carried out with a finishing temperature of the hot finish rolling to Ar ₃ or more. In order to refine the grain size of the cold rolled steel sheet, it is effective to refine the grains of the hot rolled sheet. For this purpose, the hot rolled temperature is preferably as low as possible, and is preferably 920 ° C or lower. However, when the hot rolling temperature is less than or equal to Ar ₃ , coarse grains occur in the surface layer of the hot-rolled sheet due to the rolling in the two-phase region of ferrite-austenite, and it becomes impossible to refine the martensite particle size d in subsequent steps. For this reason, the hot finish rolling temperature is preferably Ar ₃ or more and 920 ° C. or less.

Although this hot-rolled steel sheet is cooled and wound up, it is preferable that the average cooling rate from 850 degreeC to 600 degreeC is 20 degreeC / sec or more in a cooling process. This is because the cooling rate from 850 degreeC to 600 degreeC is important in order to thin the particle diameter of the crystal | crystallization of a hot rolled sheet steel. If the average cooling rate is slower than 20 ° C./sec in this temperature range, the particle diameter becomes large, and therefore it cannot be refined thereafter. Winding temperature is 750 degrees C or less, Preferably it is 550 degrees C or less. This is because if the coiling temperature is higher than this, the layered structure of ferrite and pearlite is formed in the hot rolling step, and uniformity is impaired. Thus, workability is deteriorated even after hot rolling or annealing.

Next, the wound steel sheet is processed to a desired sheet thickness within the range of 0.1 to 0.5 mm by cold rolling. However, in the present invention, it is important to make the cold rolling rate in this cold rolling a large value of 80% or more. If this cold rolling rate is less than 80%, the ferrite grain size at the time of annealing becomes large, and martensite cannot be made into a predetermined | prescribed fine grain. In addition, in view of the performance of the cold rolling mill, it is difficult to set the cold rolling rate to 95% or more. Therefore, the cold rolling rate is in the range of 80 to 95%, preferably 83 to 93%.

The following annealing and quenching are important processes for obtaining the composite structure of ferrite and martensite. In the annealing step, the cold rolled steel sheet is held at a temperature of Ar ₁ or more and 870 ° C. or less for 3 minutes or less. If the holding temperature is less than or equal to Ar _1, no austenite transformation occurs in the annealing step, so martensite cannot be formed even if it is quenched. However, when the holding temperature is 870 ° C or higher, recrystallization at the time of annealing proceeds so that the ferrite becomes granulated and martensite cannot be made smaller than a predetermined size. In addition, the holding time of 3 minutes or more is for suppressing the progress of recrystallization.

In the final cooling step, fine martensite can be precipitated in the ferrite by cooling the temperature range from 750 ° C to 400 ° C at a cooling rate of 100 ° C / sec or more to 300 ° C or less. If the cooling rate is slower than this, no martensite is formed. In addition, the temperature range for cooling at a cooling rate of 100 ° C./sec or higher from 750 ° C. to 400 ° C. is most effectively used to precipitate martensite. When the quenching start temperature is lower than 750 ° C., ferrite grows and martens The refinement of the site becomes difficult. In addition, if quenching is not carried out to at least 400 degreeC, martensite will not be produced | generated and it will become insufficient in strength. In this way, when cooling to 300 degrees C or less, a crystal structure is stabilized and the high strength steel sheet for steelmaking of the present invention which the fine martensite particle disperse | distributed in ferrite can be obtained. In addition, the cooling rate in the temperature range of 400 degrees C or less is arbitrary.

The high strength steel sheet for steel production manufactured in this way is equipped with the martensite particle diameter d of 1st, 2nd invention, and can satisfy both strength and ductility. Moreover, the alloy component satisfies ASTM and can be used safely as a raw material of food cans and beverage cans. Examples of the present invention are shown below.

(Example 1)

Calculation result of the state of martensite and the left side of Formula <A> about the steel plates A1 to S1 which melted the steel of the component shown in Table 1, and manufactured on the manufacturing conditions shown in Table 2 and Table 3 (continuity of Table 2). , 30T hardness, and stretching were evaluated.

Here, about the state of martensite, martensite is identified by leveler etching, image analysis is carried out over a visual field of 0.2 micrometer x 0.2 micrometer over at least 100 visual field with a 1000-times optical microscope, and a martensite fraction (martensite which occupies a structure | tissue) Find the site area ratio). In addition, the martensite particle diameter calculates and averages a circular equivalent diameter by the same measurement.

Hardness is evaluated based on 30T of JIS 2245. If the 30T hardness is less than 60, the strength is insufficient when used in the body portion of the can as described above, so that 60 or more is passed. Drawing performed the material test based on JIS No. 5 of JIS Z2241, making it pass that 5% or more of extending | stretching was mentioned above, and made less than 5% the rejection as mentioned above.

It can be seen from Table 2 and Table 3 (continued in Table 2) that steels satisfying predetermined conditions by components, hot rolling, cold rolling, and annealing, and satisfying the formula <A> have a small martensite particle diameter and are secured in stretching. have.

(Example 2)

The result of calculation of the state of martensite and the left side of Formula <B> about the steel plates A21-Q22 which produced the steel of the component shown in Table 1 by the manufacturing conditions shown in Table 4 and Table 5 (continuity of Table 4), The ultramicro | Vickers hardness, 30T hardness, and extending | stretching were evaluated.

In addition, various evaluation methods were performed by the same method and reference | standard as Example 1, and the martensite ultra-microbe Vickers hardness was measured by the measurement load as 0.1 gf by Shimadzu Corporation HMV-1AD.

From Table 4 and Table 5 (continued in Table 4), it can be seen that the steels satisfying the formula <B> by satisfying predetermined conditions by hot rolling, cold rolling, and annealing have a small martensite particle diameter and are secured in stretching.

Claims (5)

In the high-strength thin steel sheet for steel pipe having a product plate thickness t of 0.1 to 0.5mm,
In mass%,
C: 0.04 to 0.13%,
Si: greater than 0.01% to 0.03%,
Mn: 0.1-0.6%,
P: 0.02% or less,
S: 0.03% or less,
Al: 0.01-0.2%
N: 0.001 to 0.02%
And the balance has a steel composition composed of Fe and unavoidable impurities, and the steel structure is a complex structure of ferrite and martensite of a ferrite main body,
The martensite fraction is 5% or more and less than 30%,
The martensite particle diameter d (µm) and the product sheet thickness t (mm) satisfy the following equation <A>,
30T high strength steel sheet for steel making, characterized in that the hardness is 60 or more.
1.0 <(1-EXP (-t × 3.0)) × 4 / d ... Expression <A> In the high-strength thin steel sheet for steel production, the product sheet thickness t is 0.1 to 0.5mm, in mass%,
C: 0.04 to 0.13%,
Si: greater than 0.01% to 0.03%,
Mn: 0.1-0.6%,
P: 0.02% or less,
S: 0.03% or less,
Al: 0.01-0.2%,
N: 0.001-0.02%,
And a balance having a steel composition composed of Fe and unavoidable impurities, the steel composition being a composite structure of ferrite and martensite of a ferrite main body,
The martensite fraction is 5% or more and less than 30%,
A high-strength steel sheet for steel pipe, characterized in that the martensite particle size d (unit µm), the product sheet thickness t (mm), and the martensite hardness (Hv) satisfy the following formula <B>, and the 30T hardness is 60 or more.
1.0 <(1-EXP (-t × 3.0)) × 2400 / Hv} / d ... Expression <B> The method according to claim 1 or 2, wherein in the steel composition, in mass%,
Mo: 0.05% or less,
Ni: 0.15% or less,
Cr: 0.10% or less,
V: 0.02% or less,
B: 0.02% or less,
Nb: 0.02% or less,
Ti: 0.02% or less,
A high strength steel sheet for steelmaking, characterized by containing one or two or more of them. Claim 1 to claim 3 the tolerance A method of manufacturing a high strength steel sheet, the finish temperature of Ar and then subjected to hot finish rolling at the ₃ or higher, and then wound at a temperature not higher than 750 ℃, rolling rate as described in any one of items Cold rolling is performed at 80% or more, and in the annealing step, after holding at least ₁ minute at a temperature of Ar ₁ or more and 870 ° C. or less, the temperature range of 750 ° C. to 400 ° C. is 300 ° C. at a cooling rate of 100 ° C./sec or more. The manufacturing method of the high strength steel sheet for steel pipes characterized by cooling to the following. The method of claim 4, wherein the finishing temperature of the hot finish rolling Ar ₃ or more, less than 920 ℃, and the above average cooling rate of 20 ℃ / sec to 600 ℃ at 850 ℃ in the cooling step after, 550 of the take-up temperature The manufacturing method of the high strength steel sheet for steel pipes characterized by below ° C.

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