JP2002161315A - Hot dip coated, high tensile strength steel sheet and strip and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot dip coated, high tensile strength steel sheet and strip that is highly tensile of its nature, nevertheless almost free from uncoated area. SOLUTION: A high tensile steel sheet and strip, the chemical composition of which is compositely added by Si in the range of 0.25-1.2 mass% that, however, must be controlled within the range to satisfy the relationship of 1.5×Si (mass%)<Mn (mass%), Ti in the amount controlled to 0.030 mass% or less, and one or more of Nb: 0.005-0.2 mass%, Cu: less than 0.5 mass%, Ni: less than 1.0 mass% and Mo: less than 1.0 mass%, but in any way in the range of 0.03-1.5 mass% in total amount, is subjected to recrystallization annealing at the temperature of 750 deg.C or higher in the reduction atmosphere with the dew point 0 deg.C or below but at -45 deg.C or higher. The steel is then cooled down and pickled to remove oxides produced over the surface. It is then reheated at the temperature of 650 deg.C or higher but at 800 deg.C or lower in the reduction atmosphere with dew point of -20 deg.C or lower, and finally in the midst of cooling down from the reheating temperature the high tensile steel sheet and strip is hot dip coated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a hot-dip galvanizing method for the surface of a high-strength steel sheet, such as zinc (including alloyed ones; the same applies hereinafter), aluminum, zinc-aluminum alloy, zinc-aluminum-magnesium alloy, and the like. The present invention relates to a high-strength hot-dip galvanized steel sheet suitable for use in an automobile body and the like, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, a hot-dip galvanized steel sheet has been used as a steel sheet for automobiles in order to achieve a reduction in weight for improving the collision safety of automobiles and improving fuel efficiency from the viewpoint of preserving the global environment. Applications of high-strength hot-dip coated steel sheets are increasing. In order to obtain such a high-strength hot-dip coated steel sheet,
It is important to use a steel sheet which has excellent plating properties and has the desired strength and workability (such as press formability) after passing through the hot-dip plating bath or after further alloying treatment. .

[0003] Generally, to increase the strength of a steel sheet, Si or Mn is added to the steel sheet. A steel sheet added with these elements is used, for example, in a continuous galvanizing line (CG).
It is known that when plating is performed using L (Continuous Galvanizing Line), oxides such as Si and Mn are generated on the surface of the steel sheet in an annealing step before plating, and the plating property is reduced.

[0004] This phenomenon is that, when annealing in a reducing atmosphere before plating, the atmosphere is reducing for Fe, but oxidizing for Si and Mn in the steel, so that the steel sheet surface This is because Si and Mn are selectively oxidized to form an oxide. Such surface oxides significantly reduce the wettability of hot-dip zinc to the steel sheet, so that the hot-dip galvanized steel sheet using a high-strength steel sheet as the base metal has reduced plating properties,
In particular, when the content of Si, Mn, or the like is high, there is a problem that plating is not performed partially, that is, non-plating occurs.

[0005] In order to improve the deterioration of the plating property of such a high-strength steel sheet, for example, Japanese Patent Application Laid-Open No. 55-122865 discloses that a steel sheet is forcibly oxidized under a high oxygen partial pressure prior to heating during plating. Later reduction methods have been proposed. Japanese Patent Application Laid-Open No. 58-104163 proposes a method of performing pre-plating before hot-dip plating. However, the former method has problems in that surface oxides are not sufficiently controlled by forced oxidation, and that stable plating properties are not necessarily guaranteed depending on the steel components and plating conditions. On the other hand, the latter method has a problem that the production cost is increased by adding an extra process.

[0006] In addition, JP-A-6-287684 discloses that
A high-strength steel sheet with improved plating properties by optimizing the amounts of P, Si and Mn has been disclosed. Also, JP-A-7-70723 and JP-A-8-85858 disclose that a surface oxide is generated by performing recrystallization annealing before plating, and this oxide is removed by pickling, followed by hot-dip galvanizing. Have been proposed. By these methods,
It has become possible to prevent the occurrence of non-plating for a considerable number of high-strength steels. However, even with these methods, there remains a problem that occurrence of non-plating cannot be completely prevented for steel types having a high Si content.

[0007]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems. Even when a high-strength steel sheet having a high Si or Mn content is used as a plating base sheet, the present invention It is an object of the present invention to propose a high-strength hot-dip coated steel sheet that can effectively prevent occurrence thereof, together with its advantageous production method.

[0008]

Means for Solving the Problems Now, the inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have restricted the amount of Ti to a predetermined range with respect to the steel component. While adding Nb and Cu, Ni, and Mo in combination, an internal oxide layer is formed just below the surface of the steel sheet by annealing in a continuous annealing line (CAL) (hereinafter referred to as recrystallization annealing). And the surface oxides generated at the same time are removed by pickling, followed by continuous hot-dip galvanizing line (CG
At the time of heating before plating in L) (hereinafter referred to as pre-plating heating), the internal oxide layer serves as a diffusion barrier,
It has been found that the generation of oxides such as Si and Mn on the surface of the steel sheet is drastically reduced, and as a result, a large improvement in plating property can be achieved. The present invention has been completed based on the above findings.

That is, the present invention relates to a high-strength hot-dip coated steel sheet having a hot-dip coating layer on the surface of the steel sheet, wherein the coated steel sheet has a C content of 0.010 mass% or less, a Si content of 0.25 mass% or more and 1.2 mass% or less. , Mn: 0.50 mass% or more, 3.0 mass%
Below, Nb: 0.005 mass% or more, 0.2 mass% or less, Ti: 0.
030 mass% or less, B: 0.005 mass% or less, Al: 0.10 mass
% Or less, P: 0.100 mass% or less, S: 0.010 mass% or less, N: 0.010 mass% or less, 1.5 × Si (mass%) <Mn
(Mass%) within the range that satisfies, and further Cu: 0.5 ma
One or more selected from less than ss%, less than 1.0 mass% Ni, less than 1.0 mass% Ni: 0.03 mass% in total
A high-strength steel sheet containing 1.5 mass% or less and the balance being Fe and unavoidable impurities.
Hereinafter, recrystallization annealing at a temperature of 750 ° C or more in a reducing atmosphere of -45 ° C or more, after cooling, removing the oxides generated on the surface of the steel sheet by pickling, and then again having a dew point of -20 ° C or less. In a reducing atmosphere of 650 ° C or higher and 850 ° C or lower,
A high-strength hot-dip coated steel sheet, which is obtained by performing a hot-dip plating process in the course of lowering the temperature from the reheating temperature.

Further, the present invention provides a method for producing a composition comprising: C: 0.010 mass% or less;
Si: 0.25 mass% or more, 1.2 mass% or less, Mn: 0.50 mass%
3.0 mass% or less, Nb: 0.005 mass% or more, 0.2 ma
ss% or less, Ti: 0.030 mass% or less, B: 0.005 mass% or less, Al: 0.10 mass% or less, P: 0.100 mass% or less, S:
0.010 mass% or less, N: 0.010 mass% or less, 1.5 × Si
(Mass%) <Mn (mass%) in a range satisfying Cu, less than 0.5 mass% of Cu, less than 1.0 mass% of Ni, and less than 1.
One or two or more selected from less than 0 mass% are contained in a total range of 0.03 mass% or more and 1.5 mass% or less,
The remainder is a high-tensile steel sheet with a composition of Fe and unavoidable impurities in a reducing atmosphere with a dew point of 0 ° C or less and -45 ° C or more.
After recrystallization annealing at a temperature of 750 ° C or higher, and after cooling, the oxides formed on the surface of the steel plate were pickled and removed, and the dew point was reduced to −
Production of a high-strength hot-dip coated steel sheet characterized by heating to a temperature of 650 ° C or higher and 850 ° C or lower in a reducing atmosphere of 20 ° C or lower, and performing a hot-dip coating process during the temperature reduction from the reheating temperature. Is the way.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is based on the concept that, after optimizing the amount of Si, the addition of Nb and Cu, Ni, or Mo is added while limiting the amount of Ti. The main feature is that an oxide layer is formed, and at this time, a surface oxide also formed on the surface of the steel sheet is removed by pickling, and then hot-dip plating is performed after heating before plating. Therefore, the reason why the composition conditions of the present invention and the manufacturing conditions such as the recrystallization annealing and the heating conditions before plating are limited to the above ranges will be described below.

First, the reason why the component composition of the high-strength steel sheet used as the plating base sheet in the present invention is limited to the above range will be described. C: 0.010 mass% or less C is desirably reduced in order to improve the elongation and r-value of the steel sheet. In particular, when the C content exceeds 0.010 mass%, even if an appropriate amount of Ti or Nb is contained, Since the effect of improving the material (especially the press formability) by the element cannot be obtained, C is limited to 0.010 mass% or less. The content is
If the content is less than 0.001 mass%, it is difficult to form an internal oxide layer by recrystallization annealing. Therefore, it is preferable that C is contained at 0.001 mass% or more.

Si: 0.25 mass% or more and 1.2 mass% or less Si is an effective element for strengthening steel, but conventionally, it is reduced as much as possible so that Si oxide is not generated on the steel sheet surface by heating before plating. I needed to. However, in the present invention, even when Si is contained in an amount of 0.25 mass% or more, an internal oxide layer of Si and Mn is formed immediately below the steel sheet surface during recrystallization annealing by adding Nb and Cu or Ni or Mo in combination. However, this suppresses generation of oxides of Si and Mn on the surface of the steel sheet in the next pre-plating heating, so that the steel of the present invention exhibits good plating properties.
It is considered that this mechanism is based on the fact that the internal oxide layer acts as a diffusion barrier against the movement of Si or Mn from inside the steel to the steel sheet surface. The above effect is achieved by 0.25 mass% of Si.
It cannot be obtained unless it contains more than the above. On the other hand, when the content exceeds 1.2 mass%, SiO ₂ is generated on the steel sheet surface during recrystallization annealing, and the surface oxide cannot be completely removed in a subsequent pickling step, and a part of the surface oxide remains, so that non-plating occurs. Occurs. Therefore, Si was limited to the range of 0.25 to 1.2 mass%.

1.5 × Si (mass%) <Mn (mass%) Also, the amount of Si is 1.5 ×
If the amount satisfies the relationship of Si (mass%) ≧ Mn (mass%), SiO ₂ is also generated on the steel sheet surface during recrystallization annealing, and this surface oxide cannot be completely removed in the subsequent pickling step. ,
Non-plating occurs. Therefore, Si is 0.25 to 1.
In the range of 2 mass%, and 1.5 × Si (mass%) <Mn (mass
%) Is important.

Mn: 0.50% by mass or more and 3.0% by mass or less Mn not only contributes to improvement of strength but also suppresses generation of SiO ₂ on the steel sheet surface during recrystallization annealing, and is easily pickled. This has the effect of generating a removable Si, Mn composite oxide. However, when the content is less than 0.50 mass%, the effect is poor. On the other hand, when the content exceeds 3.0 mass%, Mn oxides are generated on the steel sheet surface during heating before plating, so that non-plating tends to occur, and the steel becomes harder. This makes cold rolling difficult. Therefore, Mn was limited to the range of 0.50 to 3.0 mass%.

Nb: 0.005 mass% or more and 0.2 mass% or less Nb reduces the crystal grains of the steel sheet generated by recrystallization annealing and promotes the formation of an internal oxide layer of Si and Mn immediately below the steel sheet surface. This contributes to improvement of plating property.
This effect cannot be obtained unless 0.005 mass% or more is contained. On the other hand, if the content exceeds 0.2 mass%, the steel is hardened, so that not only hot rolling and cold rolling become difficult, but also the recrystallization temperature is increased to make recrystallization annealing difficult and surface defects are generated. . Therefore, Nb was limited to the range of 0.005 to 0.2 mass%.

Ti: 0.030 mass% or less Ti forms carbon / nitride and effectively contributes to the improvement of workability of steel. Therefore, Ti is contained as necessary. However, if contained excessively, Si and Mn generated during recrystallization annealing
Increases the surface oxides, making it difficult to pickle and remove such oxides. Therefore, the amount of Ti is limited to 0.030 mass% or less. This Ti does not necessarily need to be contained.

B: 0.005 mass% or less B is an element effective for improving the resistance to secondary working embrittlement, but its effect cannot be expected even if it is contained in excess of 0.005 mass%. Instead, it causes deterioration. Further, if it is contained excessively, the hot ductility is reduced. Therefore,
B contains 0.005% by mass as the upper limit. The lower limit of the content is not particularly limited, but may be included depending on the required degree of improvement in the resistance to secondary working brittleness, and is usually 0.
It is desirable to contain 0010 mass% or more.

Al: 0.10 mass% or less Al not only contributes as a deoxidizer in the steelmaking stage, but also
It is also useful as an element for fixing N that causes aging deterioration as AlN. However, when the content exceeds 0.10% by mass, not only the production cost is increased but also the surface properties are deteriorated. Therefore, the content of Al is set to 0.10% by mass or less. Preferably it is 0.050 mass% or less. If the content is less than 0.005 mass%, a sufficient deoxidizing effect is hardly expected, so the lower limit of the Al content is preferably set to 0.005 mass%.

P: 0.100 mass% or less Inclusion of P increases the strength. However, when the content exceeds 0.100 mass%, segregation at the time of solidification becomes extremely remarkable. As a result, the increase in strength is saturated, and the workability is deteriorated. It causes significant deterioration, and becomes practically unusable. Therefore, P was limited to 0.100 mass% or less. In the case of galvannealing, the amount of P is preferably set to 0.060 mass% or less because alloying is delayed. However, since it is costly to make it less than 0.001 mass%, it is advantageous to set P to 0.001 mass% or more.

S: not more than 0.010 mass% S causes hot cracking at the time of hot rolling and also causes fracture in the nugget of the spot welded portion. Therefore, it is desirable to reduce S as much as possible. In addition, in alloying treatment after hot-dip galvanizing, it may cause alloying unevenness. Therefore, it is desirable to reduce as much as possible from this aspect. The reduction in the amount of S contributes to an improvement in workability due to a reduction in S precipitates in steel and an increase in the amount of Ti effective for fixing C. Therefore, S is
Limit to less than 0.010 mass%. More preferably 0.005mas
s% or less.

N: 0.010 mass% or less N should be reduced as much as possible in order to secure materials such as ductility and r value. Especially N content is 0.010 mass%
Below, a satisfactory effect can be obtained.
0.010 mass%. Preferably it is 0.0050 mass% or less. Nevertheless, suppressing N to less than 0.0005 mass% increases the cost, so the lower limit is preferably set to 0.0005 mass%.

Cu: less than 0.5 mass%, Ni: less than 1.0 mass%, Mo: less than 1.0 mass%, and the total of these is 0.03 ma.
ss% or more and 1.5 mass% or less Cu, Ni and Mo all promote the formation of internal oxide layers of Si and Mn immediately below the surface of the steel sheet during recrystallization annealing. Since the formation of oxides of Mn and Mn is suppressed, the steel of the present invention exhibits good plating properties. This effect cannot be obtained unless one or more selected from these elements are contained in a total of 0.03 mass% or more. On the other hand, the total exceeds 1.5 mass%, or
Cu content is 0.5 mass% or more, Ni content is 1.0 mass% or more, Mo content is
If it exceeds 1.0 mass%, the surface properties of the hot-rolled sheet become poor. Therefore, Cu: less than 0.5 mass%, Ni: less than 1.0 mass%, Mo: less than 1.0 mass%, and a total of one or more selected from Cu, Ni, and Mo is 0.03 mass% or more;
The content was set to 1.5 mass% or less.

Next, the reason why the recrystallization annealing conditions and the heating conditions before plating are limited to the above ranges will be described. In the method for producing a hot-dip coated steel sheet according to the present invention, the steps up to recrystallization annealing, that is, the hot rolling step and the cold rolling step are not particularly limited, and these steps may be performed according to a conventional method. Recrystallization annealing Recrystallization annealing releases the strain introduced during cold rolling by heating (usually using CAL) above the recrystallization temperature, and imparts the necessary mechanical properties and workability to the steel sheet. In addition to the role of, an inner oxide layer of Si or Mn is formed just below the surface of the steel sheet. This is because the presence of such an internal oxide layer does not cause generation of oxides of Si or Mn on the surface of the steel sheet during subsequent heating before plating, thereby suppressing the occurrence of non-plating.

Here, if the recrystallization annealing is lower than 750 ° C., the formation of the internal oxide layer is insufficient and good plating properties cannot be expected, so the recrystallization annealing must be performed at 750 ° C. or higher.
The recrystallization annealing needs to be performed in a reducing atmosphere having a dew point of 0 ° C. or less and −45 ° C. or more. Because the dew point is 0
If the temperature is higher than ℃, the oxides are mainly Fe oxides and the internal oxide layer of Si or Mn is difficult to be generated. This is because it is difficult to generate an internal oxide layer. The reducing atmosphere may be a nitrogen gas, an argon gas, a hydrogen gas, a carbon monoxide gas alone or a mixture of two or more of these gases. The temperature history of the recrystallization annealing was as follows: after holding at 800 to 900 ° C for 0 to 120 seconds,
A pattern of cooling at a rate of about 0 ° C./s is preferred.

Pickling removal of surface oxide layer Formed on steel sheet surface by recrystallization annealing in reducing atmosphere
Pickling is performed to remove oxides of Si and Mn. As the pickling solution, it is preferable to use 3 to 20 mass% hydrochloric acid, and it is preferable that the pickling time is about 3 to 60 seconds.

Pre-plating heating After removing Si and Mn oxides on the steel sheet surface by pickling,
Heat before plating. Usually, this heating before plating is CGL
May be used. And this pre-plating heating has a dew point:
The test shall be performed at a temperature of 650 ° C or more and 850 ° C or less in a reducing atmosphere of -20 ° C or less. Because the dew point is -20 ° C
If the atmosphere is higher, a thick Fe oxide is generated on the surface of the steel sheet, which causes deterioration in plating adhesion. If the annealing temperature is lower than 650 ° C, the steel sheet surface is not activated, and the reactivity between the molten metal and the steel sheet is not always sufficient.On the other hand, if the temperature exceeds 850 ° C, surface oxides of Si and Mn are formed again on the steel sheet surface. And
This is because non-plating occurs. The atmosphere is not necessarily a reducing atmosphere throughout the entire process, and the stage in which the steel sheet is heated to 400 to 650 ° C is an oxidizing atmosphere, and only the temperature range above that temperature is a reducing atmosphere. A method may be used. Further, the reducing atmosphere may be a nitrogen gas, an argon gas, a hydrogen gas, a carbon monoxide gas alone or a mixture of two or more of these gases. In addition, the temperature history at the time of heating before plating was as follows: after holding at 700 to 800 ° C for 0 to 180 seconds,
A pattern of cooling at a rate of about 100 ° C./s is preferred.
Further, in the pre-plating heating, it is not necessary to control the mechanical properties, and it is only necessary to heat the plating base sheet required before the hot-dip plating, but the mechanical properties are controlled using the pre-plating heating. Needless to say, it may be.

Hot-dip plating Next, in the present invention, hot-dip plating is performed during the cooling from the above-mentioned pre-plating heating, but this plating method is not particularly limited, and may be carried out according to a conventionally known method. For example, in the case of hot-dip galvanizing,
The steel sheet heated before plating is immersed in a hot-dip zinc bath having a bath temperature of about 460 to 490 ° C. to perform hot-dip plating. At this time, it is preferable that the temperature of the sheet when it is immersed in the bath is about 460 to 500 ° C. The steel sheet immersed in the molten zinc bath in this way is
After being lifted out of the bath, the amount of coating is adjusted by gas wiping or the like, and a hot-dip galvanized steel sheet is obtained. Furthermore, such a hot-dip galvanized steel sheet can be made into a galvannealed steel sheet by performing a heat alloying process thereafter.

The other hot-dip plating treatments include:
There are hot-dip aluminum plating, hot-dip zinc-aluminum plating, hot-dip zinc-aluminum-magnesium plating, and the like. These may be subjected to hot-dip plating according to a conventionally known method. The amount of hot-dip coating is preferably about 20 to 100 g / m ² per side.

[0030]

Next, an embodiment of the present invention will be described. Steel slabs having various component compositions shown in Table 1 were heated to 1200 ° C.
Finish rolling temperature: hot rolling was performed at 850 to 900 ° C. Next, after pickling this hot-rolled steel strip, it is cold-rolled at a draft of 77% to form a cold-rolled sheet having a thickness of 0.7 mm, and recrystallized using CAL and CGL under the conditions shown in Table 2. Annealing-pickling-
A process for a pre-plating heating-dipping process was performed.
The atmosphere gas used in recrystallization annealing was (7 vol% H ₂
+ N ₂ ) gas and heating before plating (5vol% H ₂ + N ₂ )
Gas was used. In particular, No. 12 pre-plating heating is performed in a combustion gas atmosphere containing 1 vol% oxygen up to 600 ° C,
At 600 ° C. or higher, the test was performed in a (10 vol% H ₂ + N ₂ ) gas atmosphere. -Hot dip galvanizing conditions Bath temperature: 470 ° C Immersion plate temperature: 470 ° C Al content: 0.14mass% Coating weight: 50 g / m ² (per side) Plating time: 1 second

From each of the hot-dip galvanized steel sheets thus obtained, 100 test pieces each having a size of 40 mm × 80 mm were sampled, and a test piece in which even one non-plated piece having a diameter of 1 mm or more was observed was rejected. . Table 2 shows the pass rate obtained from the ratio of the pass count.

[0032]

[Table 1]

[0033]

[Table 2]

As is clear from Table 2, all the inventive examples have better plating properties than the comparative examples. In addition, for Invention Examples 1 and 3, at 490 ° C.
The alloying treatment was performed for 60 seconds, but no occurrence of uneven alloying was observed.

[0035]

As described above, according to the present invention, various hot-dip galvanized steel sheets including a hot-dip galvanized steel sheet which hardly generates non-plating can be stably obtained even though the steel sheet is a high-tensile steel sheet. Accordingly, by providing the steel sheet of the present invention as an automobile steel sheet, the weight and fuel economy of the automobile are significantly improved.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C23C 2/40 C23C 2/40 (72) Inventor Kazuo Mochizuki 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation F-term in the Technical Research Institute (Reference) 4K027 AA02 AA05 AA23 AB02 AB42 AC12 AE11 4K037 EA01 EA02 EA04 EA13 EA15 EA16 EA17 EA18 EA19 EA20 EA23 EA25 EA27 EA28 EA31 EB06 EB08 FA03 F04 FJ06 F05 F05

Claims (2)

[Claims] 1. A high tension hot-dip coated steel sheet having a hot-dip coating layer on the surface of the steel sheet, wherein the coated steel sheet is: C: 0.010 mass% or less, Si: 0.25 mass% or more, 1.2 mass% or less, Mn: 0.50 mass% or more, 3.0 mass% or less, Nb: 0.005 mass% or more, 0.2 mass% or less, Ti: 0.030 mass% or less, B: 0.005 mass% or less, Al: 0.10 mass% or less, P: 0.100 mass% or less, S : 0.010 mass% or less, N: 0.010 mass% or less in a range satisfying 1.5 x Si (mass%) <Mn (mass%), and further, Cu: less than 0.5 mass%, Ni: less than 1.0 mass%, Mo: One or more selected from less than 1.0 mass% 0.03 mass in total
% And 1.5 mass% or less, with the balance being Fe and unavoidable impurities.
After recrystallization annealing at a temperature of 750 ° C or higher in a reducing atmosphere of -50 ° C or lower and -45 ° C or higher, after cooling, oxides generated on the surface of the steel sheet are removed by pickling, and the dew point is again -20 ° C. High tensile melting obtained by heating to a temperature of 650 ° C or higher and 850 ° C or lower in the following reducing atmosphere and subjecting to a hot-dip plating process in the course of lowering the temperature from this reheating temperature. Plated steel sheet. 2. C: 0.010 mass% or less, Si: 0.25 mass% or more, 1.2 mass% or less, Mn: 0.50 mass% or more, 3.0 mass% or less, Nb: 0.005 mass% or more, 0.2 mass% or less, Ti: 0.030 mass% or less, B: 0.005 mass% or less, Al: 0.10 mass% or less, P: 0.100 mass% or less, S: 0.010 mass% or less, N: 0.010 mass% or less, 1.5 × Si (mass%) <Mn (Mass%) in a range satisfying Cu, less than 0.5 mass%, less than 1.0 mass%, less than 1.0 mass%, and less than 1.0 mass% of Mo.
% And 1.5 mass% or less, with the balance being Fe and unavoidable impurities.
After recrystallization annealing at a temperature of 750 ° C or higher in a reducing atmosphere of -50 ° C or lower and -45 ° C or higher, after cooling, oxides generated on the surface of the steel sheet are removed by pickling, and the dew point is again -20 ° C. A method for producing a high-strength hot-dip coated steel sheet, comprising heating to a temperature of 650 ° C. or more and 850 ° C. or less in a reducing atmosphere described below, and performing a hot-dip coating process during the temperature reduction from the reheating temperature.