JP4644077B2 - Hot-dip galvanized high-strength steel sheet and alloyed hot-dip galvanized high-strength steel sheet excellent in corrosion resistance and formability, and methods for producing them - Google Patents

Description

  The present invention relates to a hot-dip galvanized high-strength steel sheet and an alloyed hot-dip galvanized high-strength steel sheet excellent in corrosion resistance and formability, which are suitable mainly for undercarriage parts and structural materials of automobiles that are used after being pressed. It relates to a manufacturing method.

  Reflecting the trend of upgrading automobiles, in order to improve the corrosion resistance and appearance of automotive parts, plating of automotive parts is progressing, and hot galvanized high-strength steel sheets are currently used for many parts. ing. Known as high-strength steel sheets having both press formability and high strength are composite-structure steel sheets having a ferrite-martensite structure, TRIP-type steel sheets containing residual austenite, and the like. Composite structure steel is a steel sheet in which island-like martensite is dispersed in ferrite, and has a low yield ratio, high tensile strength, and excellent elongation properties, but the interface between ferrite and martensite is the origin of fracture. Therefore, there is a drawback that the hole expandability is inferior. In addition, the steel sheet containing retained austenite produces retained austenite in the structure, and this retained austenite exhibits excellent ductility by induction transformation during work deformation, but it is also inferior in hole expandability. was there.

Therefore, as a means for improving such defects, Patent Documents 1 to 3 disclose TRIP-type hot-dip galvanized high-strength steel sheets having excellent hole expansibility and formability. However, in the conventional continuous casting, since the average cooling rate in the middle part of the slab (1/4 t position of the slab of thickness t) was as small as about 0.1 ° C./sec, the growth of dendrite is large. Mn microsegregation was large. This micro-segregation portion is elongated during rolling to form a Mn band, and this portion has a low Ms point, so that the retained austenite is unevenly distributed in the TRIP type steel sheet. As a result, stress was concentrated at the interface between martensite and ferrite, which was induced by cold working, and fracture was likely to occur. As described above, in the conventional TRIP-type hot dip galvanized high-strength steel sheet, the structure non-uniformity caused by the Mn band has been a factor that hinders formability, particularly local ductility.
Japanese Patent Application Laid-Open No. 11-296991 Japanese Patent Laying-Open No. 2005-200694

  It is an object of the present invention to provide a TRIP type hot-dip galvanized high-strength steel sheet and alloyed hot-dip galvanized high-strength steel sheet, which have a more uniform structure than the conventional, and have excellent corrosion resistance and formability, and a method for producing them. To do.

  As a result of intensive research, the inventors of the present invention have remarkably improved hole expandability by reducing the microsegregation of Mn generated during solidification and refining the band-like structure caused by Mn segregation formed after rolling. The inventors have found that it can be improved, and have completed the present invention.

The hot-dip galvanized high-strength steel sheet having excellent corrosion resistance and formability according to the present invention is represented by mass%.
C: 0.05-0.25%, Si: 2.0% or less, Mn: 0.8-3%, P: 0.0010-0.1%, S: 0.0010-0.05%, N: 0.0010 to 0.010%, Al: 0.01 to 2.0%, a hot-dip galvanized high-strength steel sheet having a steel composition consisting of iron and inevitable impurities,
The structure contains 3% or more of retained austenite with an average carbon content of 0.9% or more,
A hot dip galvanizing is performed on a steel sheet in which Mn microsegregation in the range of 1 / 8t to 3 / 8t of the sheet thickness t satisfies the formula (1).
0.10 ≧ σ / Mn (1)
Here, Mn is an addition amount, and σ is a standard deviation in Mn microsegregation measurement.

In the above-described invention, during the steel composition,
Cr: 0.01-5%, Mo: 0.01-5%, Ni: 0.01-5%, Cu: 0.01-5%, Co: 0.01-5%, W: 0.01 Can contain -5% of one or more,
Further during the steel composition
One or two or more of Ti, Nb, Zr, Hf, Ta, V can be contained alone or in total, 0.001-1% in total,
Further during the steel composition
0.0001-0.0050% of B can be contained,
Further during the steel composition
One or more of Mg, Ca, Y, and REM can be contained in an amount of 0.0001 to 0.5%.

In addition, the alloyed hot-dip galvanized high-strength steel sheet excellent in corrosion resistance and formability of the present invention is
The galvanized high-strength steel sheet according to any one of claims 1 to 5 is subjected to an alloying treatment to form an alloyed galvanized layer on the steel sheet surface.

In addition, the hot-dip galvanized high-strength manufacturing method excellent in corrosion resistance and formability of the present invention is
A hot-dip galvanized high-strength steel sheet manufacturing method for manufacturing the hot-dip galvanized high-strength steel sheet according to claim 1 from a slab,
The slab that is in the process of being cooled after continuous casting is cooled as it is or 1100 after cooling between the liquidus temperature and the solidus temperature at an average cooling rate at 1/4 t of the slab thickness t of 100 ° C / min or higher. Reheat above ℃,
Next, hot rolling is performed at a finishing temperature of 850 to 970 ° C., and then cooling is performed at an average cooling rate of 10 to 100 ° C./sec to a temperature range of 650 ° C. or less. Without steel plate,
The hot-rolled steel sheet is pickled and then cold-rolled with a rolling reduction of 40% or more, and annealed at a maximum temperature of 0.1 × (Ac ₃ -Ac ₁ ) + Ac ₁ or more and Ac ₃ + 50 ° C. or less, and then 0. It is cooled to a temperature range of 350 ° C. or more and 500 ° C. or less at an average cooling rate of 1 to 100 ° C./sec. It is characterized by being immersed in a galvanizing tank.

In addition, the manufacturing method of the galvannealed high-strength steel sheet having excellent corrosion resistance and formability according to the present invention is as follows.
The hot-dip galvanized high-strength steel sheet produced by the method according to claim 7 is subjected to an alloying treatment at a temperature of 500 to 580 ° C.

Since the hot-dip galvanized high-strength steel sheet of the present invention has a small Mn microsegregation, a Mn band in which the Mn segregation is extended in the rolling direction is less likely to occur. For this reason, since the martensite formed in the Mn band can be made fine and the structure can be made uniform, the formability can be made better than the conventional hot-dip galvanized high-strength steel sheet. Moreover, since the hot dip galvanized layer is formed on the steel plate surface, it is excellent in corrosion resistance.
Moreover, since the alloyed hot-dip galvanized high-strength steel sheet of the present invention has an alloyed hot-dip galvanized layer formed on the steel sheet surface having a small Mn band, the formability is good and the corrosion resistance is excellent.

In addition, the method for producing a hot-dip galvanized high-strength steel sheet according to the present invention produces a hot-rolled steel sheet from a slab with an increased cooling rate during solidification, so that the solidification structure is made finer than that of a normal slab and Mn microsegregation is performed. It can be small. For this reason, since a Mn band is small, a retained austenite can be made to remain uniformly, so that a hot-dip galvanized high-strength steel sheet having better formability than before can be produced.
Moreover, since the alloying process is performed on the hot-dip galvanized high-strength steel sheet manufactured by the above-described method, the Mn band is smaller and the formability is better than the conventional method.

The high-strength steel sheet having excellent formability according to the present invention is characterized in that the microsegregation of Mn in the range of 1 / 8t to 3 / 8t of the sheet thickness t satisfies the formula (1).
0.10 ≧ σ / Mn (1)
Here, Mn is an addition amount, and σ is a standard deviation in Mn microsegregation measurement. The standard deviation σ was obtained from Mn concentration distribution data obtained by performing line analysis in the plate thickness direction on a sample having a plate thickness polished using EPMA (X-ray microanalyzer).

When σ is 0.10 <σ / Mn, Mn microsegregation is not sufficiently small. For this reason, since the Mn microsegregation is stretched in the rolling direction to form a Mn band, the steel structure cannot be made uniform and a hot-dip galvanized high-strength steel sheet having excellent formability cannot be obtained. . Therefore, the microsegregation of Mn needs to satisfy the relationship of 0.10 ≧ σ / Mn. When the demand for formability is high, it is desirable that the microsegregation satisfies the formula (2). This is because the structure can be made more uniform and the moldability can be improved.
0.05 ≧ σ / Mn (2)

  The hot-dip galvanized high-strength steel sheet of the present invention is characterized in that the structure contains 3% or more of retained austenite having an average carbon content of 0.9% or more. That is, the high-strength steel sheet contains 3% to 20% of metastable retained austenite in the composite structure of ferrite and bainite. In order to cause the TRIP phenomenon and improve the moldability, 3% or more of retained austenite is essential. On the other hand, if the retained austenite exceeds 20%, a large amount of martensite is present, which may cause problems in secondary formability and impact properties. The retained austenite must have an average carbon content of 0.9% or more. If it is less than 0.9%, the stability of austenite is insufficient and the TRIP phenomenon is caused, and the moldability cannot be improved.

The reason for limiting the chemical components of the hot-dip galvanized high-strength steel sheet according to the present invention will be described below.
C is an austenite stabilizing element and is an important element for producing retained austenite. C moves from ferrite to austenite in the two-phase coexistence temperature range and the bainite transformation temperature range, and increases its stability. As a result, stable austenite remains after cooling to room temperature, which leads to a large elongation. If the C content is less than 0.05%, retained austenite having an appropriate stability cannot be obtained. On the other hand, if it exceeds 0.25%, a large amount of retained austenite is obtained, but the weldability is lowered. Therefore, the range of C in the present invention is 0.05 to 0.25% or less.

  Si is an important element for stabilizing the retained austenite. By suppressing the precipitation of carbides during bainite transformation, 0.9% or more of C is concentrated in the untransformed austenite phase, and the Ms point. Is reduced to below room temperature. It is also important as a deoxidizing element. In order to exert such an effect, it is necessary to add Si in an amount of 0.01% or more. However, if it exceeds 2.0%, the ductility is lowered and chemical conversion is performed. Since the processability also decreases, the upper limit is made 2.0%.

  Mn is necessary for stabilizing austenite and enhancing the hardenability of the steel to increase the strength. For this purpose, it is necessary to add 0.8% or more of Mn. However, if it exceeds 3%, the elongation is lowered, and the Mn band becomes prominent and the workability is lowered. Therefore, Mn is set to 0.8 to 3.0%. In addition, 0.8 to 2.0% is desirable from the viewpoint of securing moldability.

  When P is contained in a large amount, it segregates to the grain boundary, so that the local ductility is deteriorated. In addition, the weldability is deteriorated. Therefore, the upper limit is made 0.1%. In addition, since reducing P unnecessarily leads to a cost increase at the time of refining in the steelmaking stage, the lower limit is made 0.0010%.

  S is an element that forms MnS and significantly deteriorates local ductility and weldability. Therefore, the upper limit is made 0.05%. Moreover, since reducing S by mischief increases refining costs, the lower limit is made 0.0010%.

  N, like C, contributes to the stabilization of austenite. For this purpose, it is necessary to contain 0.0010% or more. However, if N is contained in excess of 0.010%, ductility and weldability deteriorate, so the upper limit is made 0.010%.

  Al is important as a deoxidizer. It is also an important additive element for promoting bainite. For this purpose, Al needs to be added in an amount of 0.01% or more. On the other hand, even if Al is added excessively, the above effect is saturated and the steel is embrittled, so the upper limit was made 2.0%. In addition, when the request | requirement of chemical conversion property is high, it is desirable to set it as 1.5% or less.

  Cr, Mo, Ni, Cu, Co, and W improve the hardenability and increase the strength of the steel, but the effect is small when the content is less than 0.01%. On the other hand, even if added over 5.0%, the effect of increasing the strength is saturated and the ductility is lowered.

  Ti, Nb, Zr, Hf, Ta, and V precipitate fine nitrides and carbides to strengthen the steel, but the effect is small at less than 0.001%. On the other hand, adding over 1% not only saturates the effect, but also reduces ductility.

  B increases the hardenability in a small amount. For this purpose, it is necessary to add 0.0001% or more, but even if added over 0.0050%, the effect is not only saturated but also the ductility is lowered. In order to exhibit such an effect of B, combined addition with Ti is effective.

  Mg, Ca, Y, and REM (rare earth elements) improve the impact characteristics and delayed fracture characteristics by controlling the shape of MnS. For this purpose, it is necessary to add one or more of these elements alone or in total to 0.0001% or more. However, excessive addition degrades moldability, so the upper limit is made 0.5%.

  In addition to the above elements, steel contains elements inevitably mixed such as Sn and As, and is made of the remaining iron.

The manufacturing method of the hot dip galvanized high strength steel sheet according to the present invention will be described below.
In producing the hot dip galvanized high strength steel sheet of the present invention, the cast slab that is being cooled after casting is cooled at an average cooling rate of 100 ° C./min or more between the liquidus temperature and the solidus temperature. Here, the average cooling rate refers to the average cooling rate in the middle part of the slab (the position of 1/4 t of the slab of thickness t). In the present invention, casting may be performed by any method as long as the cooling rate during solidification can be higher than 100 ° C./min. For example, the thickness of the slab may be reduced in continuous casting, the size of the ingot may be reduced in ingot casting, or a surface layer portion having a high cooling rate may be cut out from a normal slab and used. When changing the thickness of the continuous cast slab, the thickness of the slab is preferably 100 to 30 mm. This is because when the thickness exceeds 100, the slab cannot be cooled at a sufficiently high cooling rate. When the thickness is less than 30 mm, the casting speed increases, causing fluctuations in the molten metal surface, breakout, etc., and stable slab casting. This is because it becomes difficult.

  In addition, when the average cooling rate between the liquidus temperature and the solidus temperature is less than 100 ° C./min, the molten steel cannot be rapidly solidified, and Mn microsegregation is reduced to 0.10. It cannot be as small as satisfying the relationship of ≧ σ / Mn. Therefore, the said average cooling rate shall be 100 degrees C / min or more. Desirably, cooling is performed at an average of 200 ° C./min or more between the liquidus temperature and the solidus temperature. Thereby, the microsegregation of Mn can be made smaller.

  The slab after cooling can be directly subjected to hot rolling. Alternatively, when it is cooled to less than 1100 ° C., it can be reheated to 1100 ° C. or higher and 1300 ° C. or lower. This is because the deformation resistance in hot rolling is large at a temperature below 1100 ° C., and the generation of scale is large at temperatures exceeding 1300 ° C., and the surface properties of the steel sheet cannot be made favorable.

  Next, hot rolling is performed at a finishing temperature of 850 to 970 ° C., and after that, the steel sheet is cooled to a temperature range of 650 ° C. or less at an average cooling rate of 10 to 100 ° C./sec. And If the finishing temperature is less than 850 ° C., (α + γ) two-phase region rolling may occur, and the shape of the plate may be impaired. On the other hand, if it exceeds 970 ° C., the austenite grain size becomes coarse and the ferrite fraction decreases. And since ductility falls, finishing temperature shall be 850-970 degreeC.

  Further, when the cooling temperature after hot rolling is higher than 650 ° C., layered pearlite is easily generated. Further, when the cooling rate is less than 10 ° C./sec, pearlite is likely to be generated, and when it exceeds 100 ° C./sec, it is difficult to control the coiling temperature. The reason why the winding temperature is set to 650 ° C. or lower is that pearlite is easily generated at a temperature higher than this, and it is difficult to obtain a uniform composite structure.

  The hot-rolled steel sheet manufactured as described above is cold-rolled with a reduction rate of 40% or more after pickling. If the rolling reduction is less than 40%, the crystal grains after annealing cannot be made fine, so the rolling reduction is made 40% or more.

Then, after annealing at a maximum temperature of 0.1 × (Ac ₃ −Ac ₁ ) + Ac ₁ or more and Ac ₃ + 50 ° C. or less, the sample is cooled to 350 to 500 ° C. at 0.1 to 200 ° C./sec. When the maximum annealing temperature is less than 0.1 × (Ac ₃ −Ac ₁ ) + Ac ₁ (° C.), the amount of austenite obtained at the annealing temperature is small, so that a desired amount of retained austenite remains in the steel sheet. I can't. Moreover, since the high annealing temperature causes the formation of a grain boundary oxide layer and the coarsening of crystal grains, the upper limit of the annealing temperature is set to Ac ₃ + 50 ° C. or lower.

  Cooling after annealing is important for promoting the transformation from the austenite phase to the ferrite phase and concentrating C in the untransformed austenite phase to stabilize the austenite. When the cooling rate is less than 0.1 ° C./sec, pearlite is generated. On the other hand, when the cooling rate exceeds 200 ° C./sec, the ferrite transformation cannot sufficiently proceed, so the cooling rate after annealing is 0.1 to 200 ° C./sec.

Cooling temperature shall be 350-500 degreeC. This is because martensite is likely to be generated at a temperature lower than 350 ° C., and it is difficult to generate bainite at a temperature higher than 500 ° C.
And a steel plate is hold | maintained for 10 to 1000 seconds in the temperature range. This is because if it is less than 10 seconds, sufficient bainite cannot be generated, and the target amount of bainite can be generated by holding up to 1000 seconds. Moreover, if it exceeds 1000 seconds, carbides are generated.

  The cold-rolled steel sheet produced as described above is immersed in a hot dip zinc plating bath for plating. The temperature of the bath is 450 to 475 ° C. If the temperature is lower than 450 ° C, the viscosity of the molten zinc is high and unsuitable for wiping, and bottom dross is likely to occur. On the other hand, if the temperature is higher than 475 ° C, zinc oxide is generated. This is because problems such as an increase in zinc and an increase in the amount of zinc evaporation occur.

  As described above, after cooling the slab at a high speed, a hot-rolled steel sheet is manufactured by controlling the temperature, and after cold-rolling and annealing the hot-rolled steel sheet, by further performing hot dip galvanizing, A hot-dip galvanized high-strength steel sheet excellent in corrosion resistance and formability can be obtained, in which microsegregation is small, the structure is uniform, and ferrite bainite contains 3% or more of retained austenite.

  The hot-dip galvanized high-strength steel sheet is subsequently alloyed at a temperature of 500 to 580 ° C. When the alloying treatment temperature is less than 500 ° C., the alloying does not proceed, or the alloying progress is insufficient and the alloyed hot-dip galvanized layer cannot be formed, and the surface of the steel sheet is workable. This is because it is covered with inferior η phase and ζ phase. In addition, when the processing temperature is higher than 580 ° C., alloying progresses too much and the plating adhesion during processing decreases.

  By alloying the hot dip galvanized high strength steel sheet as described above, an galvannealed high strength steel sheet having excellent corrosion resistance and formability can be obtained.

Hereinafter, the present invention will be described in detail based on examples.
Steels having chemical components shown in Table 1 that were melted in a converter or a laboratory were cast. At this time, the cooling rate of the solidus temperature was changed as shown in Table 2 from the liquidus temperature at the 1/4 t portion of the slab. These slabs were hot-rolled steel sheets, cold-rolled, and hot-dip galvanized and alloyed to produce alloyed hot-dip galvanized high-strength steel sheets and investigated various properties. Production conditions and material properties are shown in Tables 2 and 3. The appearance before the corrosion resistance test was evaluated based on the degree of occurrence of non-plating, scratches and patterns based on the defect occurrence rate on the surface of the hot dip galvanized steel sheet. In addition, the corrosion resistance test was made by scratching the surface of the sample after plating with a cutter knife with a length of 1 cm, repeating a dry / wet cycle test up to 10 cycles, and again evaluating the external appearance based on the degree of rusting in five stages. In each of the grades 1 to 5, the appearance of plating was evaluated by visual observation or using a magnifying glass or a microscope for the state of occurrence of non-plating, the state of occurrence of defects of scratches and patterns, and the form of corrosion products. The evaluation index is as follows.
Score 5: No plating, scratches and patterns, almost no rust after corrosion test Score 4: No plating, scratches, patterns, rust after corrosion test (less than 10% in area ratio)
Score 3: Non-plating, scratches and patterns, rusting after corrosion test is small (over 10% in area ratio)
Score 2: Unplated, scratches and patterns, many rusting after corrosion test (area ratio exceeds 50%)
Grade 1: The plating did not get wet or rust occurred on the entire surface after the corrosion test.

Ac ₁ and Ac ₃ were determined from the following equations. (Reference: “Steel Material Science”: W. C. Leslie, translated by Kouda Naruse, Maruzen P273)
_{Ac 1 = 723-10.7 × Mn% -16.9} × Ni% + 29.1 × Si% + 16.9 × Cr% + 6.38 × W%.
Ac ₃ = 910−203 × √ (C%) − 15.2 × Ni% + 44.7 × Si% + 104 × V% + 31.5 × Mo% + 13.1 × W% −30 × Mn% −11 × Cr % + 20 × Cu% + 700 × P% + 400 × Al%.

In Table 3, the volume fraction of retained austenite and its carbon concentration were experimentally determined by X-ray analysis as described in JP-A-11-193435. That is, the volume fraction Vγ of retained austenite can be calculated from the data obtained using the Mo—Kα ray by the following equation.
Vγ = (2/3) {100 / (0.7 × α (211) / γ (220) +1)} + (1/3) {100 / (0.78 × α (211) / γ (311) +1)}
However, α (211), γ (220), α (211), and γ (311) indicate surface strength.

The carbon concentration Cγ of retained austenite is obtained by calculating the lattice constant (unit: angstrom) from the reflection angles of the (200) plane, (220) plane, and (311) plane of austenite by X-ray analysis using Cu-Kα ray. It can be calculated according to the formula.
Cγ = (lattice constant−3.572) /0.033

Hereinafter, the test results will be described.
Steel types A to I are steels whose chemical components are within the scope of the present invention. On the other hand, the steel type CA has Mn higher than the range of the present invention. For this reason, ductility was insufficient and cracks occurred during cold rolling, and as shown in treatment number 22, the appearance score was low.
Steel grade CB is higher than Cr and Mo, steel grade CC is higher than Ti and Nb, steel grade CD is higher than B and REM. For this reason, as shown in treatment numbers 23, 24 and 25, cracks frequently occurred during hot rolling.

  For the treatment numbers 3, 5, 8, 14, 18, and 21, the steel type has a chemical component within the scope of the present invention, but in cooling the slab during casting, the liquidus temperature is changed to the solidus temperature. The cooling rate during this period is significantly smaller than 100 ° C./min. For this reason, the index σ / Mn of Mn microsegregation was larger than 0.1, and a Mn band was formed and the structure became non-uniform, so that the steel sheet had a low elongation.

The thing of the process number 9 has the finishing temperature of hot rolling low, and a coiling temperature is higher than the range of this invention. For this reason, residual austenite cannot be left and the elongation of the steel sheet is small.
The thing of the process number 10 has a low maximum temperature of annealing, and the stop temperature of cooling is high. Therefore, the retained austenite cannot be left, and the steel sheet has low strength and ductility.

  For the comparative examples as described above, those of treatment numbers 1, 2, 4, 6, 7, 11, 13, 15, 16, 17, 19, and 20 have the appropriate chemical composition of the test steel. Since various conditions such as slab cooling, hot rolling, annealing, plating, etc. were within the scope of the present invention, Mn microsegregation was small, and an appropriate amount of retained austenite could be secured in the ferrite and bainite structures. . As a result, it was possible to produce an alloyed hot-dip galvanized high-strength steel sheet having high appearance and rusting scores and excellent balance between strength and ductility.

Claims (8)

In mass%
C: 0.05-0.25%, Si: 2.0% or less, Mn: 0.8-3%, P: 0.0010-0.1%, S: 0.0010-0.05%, N: 0.0010 to 0.010%, Al: 0.01 to 2.0%, a hot-dip galvanized high-strength steel sheet having a steel composition consisting of iron and inevitable impurities,
The structure contains 3% or more of retained austenite with an average carbon content of 0.9% or more,
Excellent corrosion resistance and formability, characterized by hot-dip galvanized steel sheets with Mn micro-segregation in the range of 1 / 8t to 3 / 8t of thickness t in the range satisfying formula (1) Hot dip galvanized high strength steel sheet.
0.10 ≧ σ / Mn (1)
Here, Mn is an addition amount, and σ is a standard deviation in Mn microsegregation measurement. Further during the steel composition
Cr: 0.01-5%, Mo: 0.01-5%, Ni: 0.01-5%, Cu: 0.01-5%, Co: 0.01-5%, W: 0.01 The hot-dip galvanized high-strength steel sheet having excellent corrosion resistance and formability according to claim 1, containing ˜5%, one or more. Further during the steel composition
It contains one or more of Ti, Nb, Zr, Hf, Ta, and V alone or in total in an amount of 0.001 to 1%, and is excellent in corrosion resistance and formability according to claim 1 or 2. Hot dip galvanized high strength steel sheet. Further during the steel composition
The hot-dip galvanized high-strength steel sheet having excellent formability, corrosion resistance and formability according to any one of claims 1 to 3, wherein B is contained in an amount of 0.0001 to 0.0050%. Further during the steel composition
The molten zinc having excellent corrosion resistance and formability according to any one of claims 1 to 4, characterized by containing one or more of Mg, Ca, Y, and REM in an amount of 0.0001 to 0.5%. Plated high-strength steel sheet.   The galvanized high-strength steel sheet according to any one of claims 1 to 5 is subjected to an alloying treatment to form an alloyed galvanized layer on the steel sheet surface, and has excellent corrosion resistance and formability Alloyed hot-dip galvanized high-strength steel sheet. A hot-dip galvanized high-strength steel sheet manufacturing method for manufacturing the hot-dip galvanized high-strength steel sheet according to claim 1 from a slab,
The slab that is in the process of being cooled after continuous casting is cooled as it is or 1100 after cooling between the liquidus temperature and the solidus temperature at an average cooling rate at 1/4 t of the slab thickness t of 100 ° C / min or higher. Reheat above ℃,
Subsequently, hot rolling is performed at a finishing temperature of 850 to 970 ° C., and after that, cooling is performed at an average cooling rate of 10 to 100 ° C./sec. Without steel plate,
The hot-rolled steel sheet is pickled and then cold-rolled with a rolling reduction of 40% or more and annealed with a maximum temperature of 0.1 × (Ac ₃ -Ac ₁ ) + Ac ₁ or more and Ac ₃ + 50 ° C. or less. Cool to a temperature range of 350 ° C. or more and 500 ° C. or less at an average cooling rate of 1 to 100 ° C./sec, then hold for 10 to 1000 seconds in the same temperature range, and then melt at 450 to 475 ° C. A method for producing a hot-dip galvanized high-strength steel sheet excellent in corrosion resistance and formability, characterized by being immersed in a galvanizing tank. An alloyed hot-dip galvanized high-strength steel sheet excellent in corrosion resistance and formability, characterized by subjecting the hot-dip galvanized high-strength steel sheet produced by the method according to claim 7 to an alloying treatment at a temperature of 500 to 580 ° C. Manufacturing method.