JP6290074B2 - High-strength cold-rolled steel sheet and high-strength galvannealed steel sheet with excellent workability - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a high-strength cold-rolled steel sheet and a high-strength galvannealed steel sheet excellent in workability, and in particular, a high-strength cold-rolled steel sheet and a high-strength alloy with improved strength-elongation balance and stretch flangeability. The present invention relates to a galvannealed steel sheet.

  High-strength cold-rolled steel sheets and galvannealed steel sheets are used for automobile frame parts. Steel sheets used as frame parts for automobiles are required to have high strength cold-rolled steel sheets and alloyed hot-dip galvanized steel sheets with high strength for the purpose of improving fuel efficiency by reducing the weight of the vehicle body. On the other hand, excellent workability is also required in order to form a complex shaped part.

  Therefore, it is possible to provide a high-strength cold-rolled steel sheet and a high-strength galvannealed steel sheet that have both high strength and enhanced elongation (total elongation; EL) and stretch flangeability (hole expansion rate: λ). For example, a steel sheet having a tensile strength (TS) of 980 MPa or more is required to have TS × EL of 25000 MPa ·% or more and λ of 20% or more.

  In order to answer the above-mentioned demand, various materials have been proposed as steel plate materials.

  For example, Patent Document 1 has a component composition similar to that of the present invention, and the steel structure in terms of area ratio, upper bainite: 50 to 90%, tempered martensite: 5 to 45%, residual austenite: 5 to 30 %, Non-tempered martensite: 5% or less (including 0%), Polygonal ferrite: 5% or less (including 0%), Among retained austenite and non-tempered martensite, the equivalent circle diameter is 1 μm or more and the average axis It is disclosed that a high-strength steel sheet having excellent elongation and stretch flangeability can be obtained by setting the coarse massive structure having a ratio (long axis / short axis) of 3 or less to 7% or less (including 0%). Has been. This high-strength steel plate is composed of upper bainite as the main phase, but by limiting the polygonal ferrite to an area ratio of 5% or less, a high-strength steel plate with a TS of 1180 MPa or more and excellent elongation, stretch flangeability, etc. The technical idea is completely different from the high-strength cold-rolled steel sheet and high-strength alloyed hot-dip galvanized steel sheet according to the present invention that require 35% or more area ratio of polygonal ferrite. Is.

  Further, in Patent Document 2, the component composition has a component composition similar to that of the present invention, the microstructure is the area ratio, the ferrite phase and the bainite phase are 10 to 93% or less, and the residual austenite phase is the area ratio of 5%. ~ 30% or less, the martensite phase is 5 to 20% or less in the area ratio, the residual austenite phase is composed of lath-like and island-like forms, the area ratio γi of the island-like residual austenite phase and the total residual austenite phase A high-strength steel sheet having an area ratio γ satisfying 0.7 ≧ γi / γ ≧ 0.3 (1) is disclosed. This high-strength steel sheet is designed to achieve both elongation and press stability by setting the retained austenite phase to the above formula (1) by setting the coiling temperature during hot rolling to 550 ° C. or lower. Is. On the other hand, the high-strength hot-dip galvanized steel sheet according to the present invention sets the coiling temperature during hot rolling to 600 to 700 ° C., limits the cold rolling rate to less than 40%, and further performs tempering. Thus, the lath-like MA (fresh martensite-residual austenite mixed structure) is formed in a predetermined ratio, and by adding a predetermined amount of tempered martensite, elongation and stretch flangeability are ensured. Therefore, the high-strength steel sheet disclosed in Patent Document 2 is different in technical idea from the high-strength cold-rolled steel sheet and the high-strength galvannealed steel sheet according to the present invention.

JP2013-72101A JP 2012-41573 A

  Therefore, the object of the present invention is to ensure that the tensile strength (TS) is 980 MPa or more, the strength-elongation balance (TS × EL) is 25000 MPa ·% or more, and the stretch flangeability (λ) is 20% or more. An object of the present invention is to provide a high-strength cold-rolled steel sheet and a high-strength galvannealed steel sheet that are excellent in strength.

The high-strength cold-rolled steel sheet excellent in workability according to the first invention of the present invention is
% By mass
C: 0.10 to 0.50%,
Si: 1.0-3.0%,
Mn: 1.0 to 3.0%
Al: 0.001 to 0.10%
Each
The balance consists of iron and inevitable impurities,
Among the inevitable impurities, P, S, and N are
P: 0.1% or less,
S: 0.01% or less,
N: each having a component composition limited to 0.01% or less,
The area ratio for all tissues
Polygonal ferrite: 35% or more,
Tempered martensite: 5% or more,
Bainitic ferrite: 5% or more
Mixed structure of fresh martensite and retained austenite (hereinafter, this mixed structure is referred to as “MA”): 5% or more,
The polygonal ferrite + the MA: a structure consisting of 80% or less in total,
Among the MAs, MAs having an aspect ratio of 3.5 or more occupy 30 to 70% of the number of all MAs.

The high-strength cold-rolled steel sheet excellent in workability according to the second invention of the present invention is
In the first invention,
Ingredient composition is further mass%,
Mo: 0.05-1.0%,
Ni: 0.05 to 1.0%,
Cu: 0.05 to 1.0%,
Cr: 0.05-1.0%
Any 1 type or 2 types or more of these are included.

The high-strength cold-rolled steel sheet excellent in workability according to the third invention of the present invention is
In the first or second invention,
Ingredient composition is further mass%,
Ti: 0.01 to 0.15%,
Nb: 0.01 to 0.15%,
V: 0.01 to 0.15%,
Zr: Any one or two or more of 0.01 to 0.15% is included.

  Moreover, the high-strength alloyed hot-dip galvanized steel sheet excellent in workability according to the fourth invention of the present invention is alloyed hot-dip zinc alloy with the high-strength cold-rolled steel sheet according to any one of the first to third inventions. A plating layer is formed.

  According to the present invention, polygonal ferrite is used as the main phase, and among the MA, the lath-like MA and the block-like MA are allowed to coexist at a predetermined ratio, thereby ensuring elongation and further adding a predetermined amount of tempered martensite. By introducing it, the stretch flangeability is improved, so that the tensile strength (TS) is 980 MPa or more, the strength-elongation balance (TS × EL) is 25000 MPa ·% or more, and the stretch flangeability (λ) is 20% or more. It is now possible to provide a high-strength cold-rolled steel sheet and a high-strength hot-dip galvanized steel sheet that have excellent workability.

It is a drawing substitute photograph which shows an example of the steel structure of the high intensity | strength cold-rolled steel plate which concerns on this invention.

  Hereinafter, the present invention will be described in more detail.

  First, the structure characterizing the high-strength cold-rolled steel sheet (hereinafter also referred to as “the steel sheet of the present invention”) excellent in workability according to the present invention will be described.

[Structure of the steel sheet of the present invention]
As described above, the steel sheet of the present invention is made of polygonal ferrite as a parent phase, into which a part of tempered martensite and bainitic ferrite is further introduced, and the stability of retained austenite is different. It is characterized by containing both MA.

<Polygonal ferrite: 35% or more>
Polygonal ferrite is a soft phase and is an effective structure for enhancing the ductility of a steel sheet. The content of polygonal ferrite with respect to the entire structure needs to be 35% or more, preferably 40% or more, more preferably 45% or more in terms of area ratio in order to ensure the ductility of the steel sheet.
The “polygonal ferrite” in the present invention is a generic term for the polygonal ferrite structure and the quasi-polygonal ferrite structure described in “Japan Steel Association Basic Research Group's“ Bainite Photograph of Steel-1 ””. Is.

<Tempered martensite: 5% or more>
By partially introducing tempered martensite, stretch flangeability can be improved while maintaining tensile strength. The tempered martensite content in the entire structure needs to be 5% or more, preferably 7% or more, more preferably 9% or more in terms of area ratio in order to ensure stretch flangeability.

<Bainitic ferrite: 5% or more>
By introducing a part of bainitic ferrite, the strength-elongation balance can be improved. The content of bainitic ferrite with respect to the entire structure needs to be 5% or more, preferably 7% or more, and more preferably 9% or more in terms of area ratio in order to ensure a strength-elongation balance.
In the present invention, “bainitic ferrite” means that the bainite structure has a lower structure having a lath-like structure with a high dislocation density, and has no carbide in the structure. Is clearly different, and is also different from a polygonal ferrite structure with a substructure with little or no dislocation density, or a quasi-polygonal ferrite structure with a substructure such as fine subgrains. Issued by the Society “Steel Bainite Photobook-1”).

<MA: 5% or more>
By partially introducing MA, the tensile strength and the strength-elongation balance can be improved. The MA content relative to the entire structure needs to be 5% or more, preferably 7% or more, and more preferably 9% or more in terms of area ratio in order to ensure tensile strength and strength-elongation balance.
Note that “MA” in the present invention is a mixed structure of fresh martensite and retained austenite, and it is difficult to separate (discriminate) fresh martensite and retained austenite by microscopic observation. Fresh martensite refers to a state in which untransformed austenite is martensitic transformed in the process of cooling the steel sheet from the heating temperature to the MS point or less, and is distinguished from tempered martensite after tempering.

<Polygonal ferrite + MA: 80% or less in total>
If the total amount of polygonal ferrite and MA is too large, the amount of tempered martensite and bainitic ferrite is insufficient, and the tensile strength cannot be secured. The total content of polygonal ferrite and MA with respect to the entire structure needs to be limited to 80% or less, preferably 79% or less, more preferably 78% or less in terms of area ratio.

<MA having an aspect ratio of 3.5 or more of the MA: 30 to 70% in terms of the number ratio with respect to all MA>
By including both lath-like (aspect ratio is 3.5 or more) MA and block-like (aspect ratio is less than 3.5) MA having different stability of retained austenite in the structure at an appropriate ratio, deformation In the first period, block-like MA with low stability of retained austenite contributes to the improvement of elongation, while in the latter stage of deformation, lath-like MA with high stability of residual austenite contributes to improvement of elongation, thereby increasing the elongation over the entire deformation (total Elongation EL) can be greatly improved. In order to effectively exhibit such an action, it is necessary to secure 30 to 70% of MA (lass-like MA) having an aspect ratio of 3.5 or more in terms of the number ratio with respect to the total MA.

[Measurement method of area ratio of each phase and aspect ratio of MA and number ratio of lath-shaped MA]
Here, each area ratio of each phase, and each measuring method of the aspect ratio and the number ratio of MA will be described.

  The area ratios of polygonal ferrite, MA, and tempered martensite were measured as follows. That is, after the steel plate was mirror-polished and corroded with 3% nital solution to reveal the metal structure, a secondary electron image of a field emission scanning electron microscope (FE-SEM) was obtained for 5 fields of about 4 μm × 3 μm region. It was observed (magnification 2000 times). An example of the observation photograph is shown in FIG. And by image analysis, the region that does not contain cementite and appears concave due to corrosion is polygonal ferrite, the region that does not contain cementite and appears to be convex on the polygonal ferrite is MA, and the region that contains cementite They were identified as tempered martensite and the respective area ratios were calculated.

  By subtracting the total area ratio of polygonal ferrite, MA and tempered martensite from 100% with the remaining structure other than “polygonal ferrite”, “MA” and “tempered martensite” as bainitic ferrite, The area ratio of nittic ferrite was calculated.

  The aspect ratio of the MA and the number ratio of the lath-shaped MA were determined by obtaining the maximum diameter and the minimum diameter individually for all the MAs identified by the secondary electron image observation of the field emission scanning electron microscope using image analysis software. The ratio (maximum diameter / minimum diameter) was calculated as an aspect ratio, and the number of MAs having an aspect ratio of 3.5 or more was determined as a lath MA, and the number ratio with respect to the total number of MAs was calculated.

[Component composition of the steel sheet of the present invention]
Below, the component composition which comprises this invention steel plate is demonstrated. Hereinafter, all the units of chemical components are mass%. In addition, “content” of each component may be simply referred to as “amount”.

C: 0.10 to 0.50%
C is an important element for improving the strength of the steel sheet. In order to exhibit the effect of improving the strength effectively, it is necessary to contain C by 0.10% or more, preferably 0.12% or more, and more preferably 0.14% or more. However, when the amount of C is excessive, coarse carbides are likely to precipitate during tempering, and the stretch flangeability is deteriorated and the weldability is also adversely affected. Therefore, the amount of C is preferably 0.50% or less, preferably Is 0.45% or less, more preferably 0.40% or less.

Si: 1.0-3.0%
Si is a useful element that has the effect of suppressing the coarsening of carbide particles during tempering, contributes to improvement in stretch flangeability, and also contributes to an increase in yield strength of the steel sheet as a solid solution strengthening element. In order to effectively exhibit such an action, it is necessary to contain Si by 1.0% or more, preferably 1.1% or more, and more preferably 1.2% or more. However, if the amount of Si becomes excessive, weldability is remarkably lowered, so the Si amount is 3.0% or less, preferably 2.9% or less, and more preferably 2.8% or less.

Mn: 1.0-3.0%
Mn, like Si, has an effect of suppressing the coarsening of cementite during tempering, contributes to the improvement of stretch flangeability, and is a useful element that also contributes to an increase in the yield strength of the steel sheet as a solid solution strengthening element. is there. Moreover, it has the effect of suppressing the ferrite transformation at the time of cooling by improving hardenability. In order to effectively exhibit such an action, it is necessary to contain Mn at 1.0% or more, preferably 1.1% or more, and more preferably 1.2% or more. However, if the amount of Mn becomes excessive, the amount of MA in the final structure becomes excessive, and conversely the stretch flangeability is lowered. Therefore, the amount of Mn is 3.0% or less, preferably 2.8% or less, Preferably it is 2.6% or less.

Al: 0.001 to 0.10%
Al is a useful element added as a deoxidizer. In order to effectively exhibit the action as a deoxidizer, it is necessary to contain Al 0.001% or more, preferably 0.003% or more, and more preferably 0.005% or more. However, if the amount of Al is excessive, the cleanliness of the steel is deteriorated, so the amount of Al is 0.10% or less, preferably 0.08% or less, and more preferably 0.06% or less.

  The steel sheet of the present invention contains the above elements as essential components, and the balance is iron and unavoidable impurities (P, S, N, O, etc.). Among the unavoidable impurities, P, S, and N are as follows: It can be contained up to each allowable range.

P: 0.1% or less P is unavoidably present as an impurity element, and contributes to an increase in strength by solid solution strengthening, but segregates at the prior austenite grain boundaries and makes the grain boundaries brittle, thereby improving the bendability. Since it deteriorates, the amount of P is limited to 0.1% or less, preferably 0.05% or less, and more preferably 0.03% or less.

S: 0.01% or less S is also unavoidably present as an impurity element, forms MnS inclusions, and becomes a starting point of a crack at the time of bending deformation, thereby lowering the bendability. % Or less, preferably 0.005% or less, more preferably 0.003% or less.

N: 0.01% or less N is also unavoidably present as an impurity element and lowers the workability of the steel sheet by strain aging. Therefore, the N content is 0.01% or less, preferably 0.005% or less, and more preferably. Is limited to 0.003% or less.

  In addition, Cr, Mo, Ti, Nb, V, B, Ni, Cu, Zr, and the like can be included as allowable components within a range not impairing the action of the present invention. Of these allowable components, Mo, Ni , Cu, Cr, Ti, Nb, V, and Zr are recommended to be contained within the following permissible ranges.

Mo: 0.05-1.0%,
Ni: 0.05 to 1.0%,
Cu: 0.05 to 1.0%,
Cr: 0.05-1.0%
Any one or two or more of these elements are useful for enhancing the hardenability and improving the strength of the steel sheet. In order to effectively exhibit the hardenability, it is recommended that the content of these elements is 0.05% or more, more preferably 0.1% or more. However, if these elements are contained excessively, the workability deteriorates and the cost increases. Therefore, the contents of these elements should be limited to 1.0% or less and further to 0.8% or less, respectively. desirable.

Ti: 0.01 to 0.15%,
Nb: 0.01 to 0.15%,
V: 0.01 to 0.15%,
Zr: Any one or more of 0.01 to 0.15% These elements are useful as precipitation strengthening elements for steel. In order to effectively exert the precipitation strengthening action, it is recommended that the content of these elements is 0.01% or more, more preferably 0.02% or more. However, if these elements are contained excessively, the workability deteriorates, so the content of these elements is preferably limited to 0.10% or less, and more preferably 0.05% or less.

  Next, preferable production conditions for obtaining the steel sheet of the present invention will be described below.

[Preferred production method of the steel sheet of the present invention]
First, steel having the above component composition is melted and formed into a slab (steel material) by ingot forming or continuous casting, followed by hot rolling (shown as “hot rolling” in Table 2 below), and a coiling temperature of 600 to The temperature is set to 700 ° C., and then cooled to room temperature to obtain a hot rolled sheet. Next, after removing the scale by pickling or the like, the hot-rolled sheet is cold-rolled (indicated as “cold-rolled” in Table 2 below) at a rolling reduction of less than 40% to obtain a cold-rolled sheet. The cold-rolled sheet is heated to a two-phase region temperature (Ac1 to Ac3) at a heating rate of 3 ° C./s or less, and is annealed by holding at this temperature (annealing heating temperature) for 50 s or more. Rapid cooling to a subcooling stop temperature of 160 ° C. or lower at a cooling rate of 25 ° C./s. Furthermore, the steel sheet of the present invention can be obtained by tempering the steel structure by reheating the annealed steel sheet and holding it at a tempering temperature of 400 to 500 ° C. for 30 to 1200 s.
The steel sheet after annealing is immersed in a galvanizing bath before reheating to the tempering temperature, and then reheated and tempered under the above conditions, while forming an alloyed galvanized layer, The steel structure of the invention steel sheet can be obtained.

  That is, the coiling temperature after hot rolling is set to 600 to 700 ° C. slightly lower than the Ar1 point, the hot rolled sheet has a coarse ferrite-pearlite structure, and the rolling reduction in subsequent cold rolling is 40%. By limiting to less than the above, by suppressing the structure of the hot rolled sheet from being refined by cold rolling, the coarse ferrite-pearlite structure is maintained as coarse as possible.

  By forming such a coarse ferrite-pearlite structure, the nucleation site of the reverse transformation from ferrite to austenite generated in the temperature rising process at a heating rate of 3 ° C./s or less to the subsequent two-phase annealing temperature can be obtained. By reducing the amount, a coarse austenite structure is formed, and a coarse ferrite-austenite structure is obtained by two-phase annealing that is maintained at a two-phase temperature of 50 s or longer. And since the crystal grain diameter in the said 2 phase region annealing is large, the diffusion rate of Mn from a ferrite to austenite becomes small, and concentration of Mn to austenite does not advance.

  Thus, in the austenite formed in the above-mentioned two-phase region annealing process, Mn concentration that suppresses bainite transformation does not occur, so that the cooling rate up to 160 ° C. or lower is 15 to 25 ° C./s. A part of austenite is transformed into bainite in the quenching process of quenching at, thereby promoting the concentration of alloying elements in the surrounding austenite and stabilizing the lath-like austenite. On the other hand, block-like austenite that is not affected by the bainite transformation does not sufficiently concentrate the alloy elements, and the stability is not improved so much. These lath and block austenites are rapidly cooled to form residual austenite, and part of the austenite is transformed into martensite during the rapid cooling process, and MA, which is a structure in which residual austenite and fresh martensite are mixed. It is formed. In particular, the fine lath-like MA generated between the laths contains a large amount of retained austenite having a high alloy element concentration and high stability, while the coarse block-like MA has a low alloy element concentration and low stability, and the fresh martensite. The percentage of sites will also be high.

  Then, among the lath-like MA and block-like MA formed in the rapid cooling process, the block-like MA having a high ratio of fresh martensite is tempered under the condition that it is maintained at a tempering temperature of 400-500 ° C. for 30-1200 s, and tempered. By forming martensite, the structure of the steel sheet of the present invention is obtained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

  Test steels having the respective component compositions shown in Table 1 below were vacuum-melted to form a slab having a thickness of 30 mm, the slab was soaked at 1150 ° C. and hot-rolled at a finishing temperature of 880 ° C. A hot-rolled sheet having a thickness of 2.5 mm was prepared by winding at the winding temperature shown in FIG. Then, after pickling this hot-rolled sheet, it cold-rolled on each condition shown in the same table 2, annealed and tempered, and produced the test steel plate.

  In addition, although description of N content was abbreviate | omitted in following Table 1, N content was an impurity level of 0.01% or less in all the steel types.

  In addition, Ac1 and Ac3 in Table 1 were determined using the following formulas (1) and (2) (see translation by Kouda Shigeyasu, “Leslie Steel Material Science”, Maruzen Co., 1985, p. 273).

Ac1 (° C.) = 723 + 29.1 [Si] −10.7 [Mn] +16.9 [Cr] −16.9 [Ni] (1)
Ac3 (° C.) = 910−203√ [C] +44.7 [Si] −30 [Mn] +700 [P] +400 [Al] +400 [Ti] +104 [V] −11 [Cr] +31.5 [Mo] −20 [Cu] -15.2 [Ni] (2)
However, [] shows content (mass%) of each element.

  About each said test steel plate, the area ratio of each phase, the aspect ratio of MA, and the number ratio of lath-like MA were measured by each measuring method demonstrated in the above-mentioned [Mode for carrying out the invention].

  Further, in order to evaluate the strength and workability of each test steel sheet, the tensile strength TS and the elongation (total elongation) EL were measured by a tensile test, and the stretch flangeability λ was measured by a hole expansion test. In addition, the tensile test produced the No. 5 test piece as described in JISZ2201, taking a long axis in the direction orthogonal to a rolling direction, and implemented according to JISZ2241. Moreover, the hole expansion test was performed in accordance with the iron standard JFST001, the hole expansion rate was measured, and this was defined as stretch flangeability λ.

  The measurement results are shown in Table 3 below. In the table, the mechanical properties (hereinafter also simply referred to as “characteristics”) of the test steel sheet satisfy all of TS: 980 MPa or more, TS × EL: 25000 MPa ·% or more, and λ: 20% or more (passed) (Circle)) and the thing which does not satisfy even one was made disqualified (x).

  As shown in Table 3 above, the steel No., which is an inventive steel (evaluation is ○). Inventive steels 1, 3, 7, 10, 18, 21, and 22 satisfy the requirements of the structure provision of the present invention as a result of being manufactured under the recommended production conditions using steel types that satisfy the requirements of the composition provision of the present invention. And the characteristics meet the acceptance criteria.

  On the other hand, steel No. which is a comparative steel (evaluation of x). 2, 4-6, 8, 9, 11-17, 19, 20, 23-27 do not satisfy at least one of the requirements of the component prescription and the structure prescription of the present invention, and the characteristics do not satisfy the acceptance criteria. .

  That is, no. 2,4-6,8,9,11-17,23, although using a steel type that satisfies the requirements of the component provisions of the present invention, because it is manufactured under conditions that partially deviate from the recommended manufacturing conditions, The organization regulations are not met and the characteristics are inferior.

  On the other hand, Steel No. Although No. 19 is manufactured under recommended manufacturing conditions, it uses a steel type that partially deviates from the requirements of the component provisions of the present invention, so it does not meet the requirements of the structure provisions and has poor properties.

  From the above results, the applicability of the present invention was confirmed.

Claims (4)

% By mass
C: 0.10 to 0.50%,
Si: 1.0-3.0%,
Mn: 1.0 to 3.0%
Al: 0.001 to 0.10%
Each
The balance consists of iron and inevitable impurities,
Among the inevitable impurities, P, S, and N are
P: 0.1% or less,
S: 0.01% or less,
N: each having a component composition limited to 0.01% or less,
The parent phase is polygonal ferrite,
The area ratio for all tissues
Polygonal ferrite: 35% or more,
Tempered martensite: 5% or more,
Bainitic ferrite: 5% or more
Mixed structure of fresh martensite and retained austenite (hereinafter, this mixed structure is referred to as “MA”): 5% or more,
The polygonal ferrite + the MA: a structure consisting of 80% or less in total,
Among the MAs, MA having an aspect ratio of 3.5 or more accounts for 30 to 70% of the total number of MAs. Ingredient composition is further mass%,
Mo: 0.05-1.0%,
Ni: 0.05 to 1.0%,
Cu: 0.05 to 1.0%,
Cr: 0.05-1.0%
The high-strength cold-rolled steel sheet excellent in workability according to claim 1, comprising one or more of the above. Ingredient composition is further mass%,
Ti: 0.01 to 0.15%,
Nb: 0.01 to 0.15%,
V: 0.01 to 0.15%,
The high-strength cold-rolled steel sheet excellent in workability according to claim 1 or 2, comprising any one or more of Zr: 0.01 to 0.15%.   A high-strength galvannealed steel sheet in which an alloyed galvanized layer is formed on the high-strength cold-rolled steel sheet according to any one of claims 1 to 3.