JP2002256448A - Method for manufacturing galvannealed steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a galvannealed steel sheet superior in a sliding property at press-forming. SOLUTION: The method for manufacturing the galvannealed steel sheet having a flat part with an area factor of 20-80% on the plated surface with an iron-zinc alloy, and an oxide layer of the thickness of 10 nm or thicker on the surface of the flat part, includes subjecting the steel sheet to hot-dip galvanizing, further alloying it with a heat treatment, temper rolling it, then contacting it with an acid solution, leaving it for 1.0-30.0 seconds after finishing contacting, washing with water, and drying it. The method also includes contacting the steel sheet with steam, before the washing and drying, and after leaving it for the 1.0-30.0 seconds. The method further includes activating the surface by contacting it with an alkaline solution, before contacting it with the acid solution and after the temper rolling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a galvannealed steel sheet having excellent slidability during press forming.

[0002]

2. Description of the Related Art Alloyed hot-dip galvanized steel sheets have better weldability and paintability than galvanized steel sheets.
It is widely used in a wide range of fields, mainly for automotive body applications. Alloyed hot-dip galvanized steel sheet for such applications is
It is press-formed and used. However, the galvannealed steel sheet has a drawback that press formability is inferior to that of a cold-rolled steel sheet. This is because the sliding resistance of the alloyed hot-dip coated steel sheet in the press die is larger than that of the cold-rolled steel sheet. That is, the galvannealed steel sheet is less likely to flow into the press die in a portion where the sliding resistance between the die and the bead is large, and the steel sheet is easily broken.

[0003] An alloyed hot-dip galvanized steel sheet is subjected to a heat treatment after galvanizing the steel sheet, thereby causing an alloying reaction in which Fe in the steel sheet and Zn in the plating layer diffuse.
This is the one in which an Fe-Zn alloy phase is formed. This Fe-Zn alloy phase is usually a film composed of a Γ phase, a δ ₁ phase, and a ζ phase,
As the concentration decreases, that is, in the order of す な わ ち phase → δ ₁ phase → Γ phase, the hardness and melting point tend to decrease. For this reason, from the viewpoint of slidability, a coating having a high hardness, a high melting point, and a high Fe concentration, in which adhesion is unlikely to occur, is effective. It is manufactured with a high average Fe concentration.

[0004] However, a film having a high Fe concentration has a problem that a hard and brittle や す く phase is easily formed at the interface between the plating and the steel sheet, and the phenomenon of peeling from the interface during processing, that is, so-called powdering is liable to occur. For this reason, JP-A-1-319661
As shown in the publication, in order to achieve both slidability and powdering resistance, a method of applying a hard Fe-based alloy as a second layer to the upper layer by a method such as electroplating has been taken. .

[0005] As a method for improving the press formability when using a galvanized steel sheet, a method of applying a high-viscosity lubricating oil is widely used. However, in this method, there are problems such as the occurrence of coating defects due to poor degreasing in the coating process due to the high viscosity of the lubricating oil, and the unstable press performance due to running out of oil during pressing. Therefore, there is a strong demand that the press formability of the galvannealed alloy itself be improved.

As a method for solving the above problem, Japanese Patent Application Laid-Open
In 53-60332 and JP-A-2-190483, an oxide film mainly composed of ZnO is formed by subjecting a surface of a galvanized steel sheet to electrolytic treatment, immersion treatment, coating oxidation treatment, or heat treatment. It discloses a technique for improving weldability or workability.

Japanese Patent Application Laid-Open No. 4-88196 discloses that a galvanized steel sheet is immersed in an aqueous solution containing 5 to 60 g / l of sodium phosphate and having a pH of 2 to 6 on the surface of a galvanized steel sheet,
Alternatively, a technique is disclosed in which an oxide film mainly composed of a P oxide is formed by applying the aqueous solution to improve press moldability and chemical conversion treatment.

[0008] Japanese Patent Application Laid-Open No. 3-91093 discloses that the surface of a galvanized steel sheet is subjected to electrolytic treatment, immersion treatment, coating treatment, coating oxidation treatment, or heat treatment to produce Ni oxide, thereby improving the press formability. A technique for improving chemical conversion treatment is disclosed.

[0009]

However, when the above prior art is applied to a galvannealed steel sheet,
The effect of improving press formability cannot be obtained stably. The present inventors have conducted a detailed study on the cause, and as a result, the alloyed hot-dip coated steel sheet is inferior in surface reactivity due to the presence of Al oxide, and due to large surface irregularities. I found that. That is, when the prior art is applied to an alloyed hot-dip coated steel sheet, the reactivity of the surface is low, so that a predetermined film is formed on the surface even when performing electrolytic treatment, dipping treatment, coating oxidation treatment, heat treatment, and the like. Is difficult, and the film thickness becomes thin in a portion having low reactivity, that is, a portion having a large amount of Al oxide. Also, due to the large irregularities on the surface, the direct contact with the press mold during press molding is the convex part of the surface, but the sliding resistance at the contact part between the thin part of the convex part and the mold is high. And the effect of improving press formability cannot be sufficiently obtained.

An object of the present invention is to solve the above problems and to provide a method for producing an alloyed hot-dip coated steel sheet having excellent slidability during press forming.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found that the thickness of the oxide layer on the surface layer of the flat portion existing on the surface of the alloyed hot-dip coated steel sheet is reduced to 10
It was found that excellent press moldability can be obtained stably by controlling it to nm or more.

The flat part on the surface of the galvannealed steel sheet exists as a convex part as compared with the surrounding area. The flat portion mainly contacts the press mold during the press forming, so that if the sliding resistance in the flat portion is reduced, the press formability can be stably improved. In order to reduce the sliding resistance in this flat part, it is effective to prevent adhesion between the plating layer and the mold. For this purpose, it is necessary to form a hard and high-melting coating on the surface of the plating layer. Is valid. As a result of study from this viewpoint, it is effective to control the thickness of the oxide layer on the surface layer of the flat portion, and by controlling the oxide film thickness of the surface layer of the flat portion, the adhesion between the plating layer and the mold does not occur. And good slidability. In addition, it has been found that a method of forming an oxide layer on a plating surface layer by contacting with an acidic solution is effective for forming such an oxide film thickness.

The present inventors have applied for a patent on a galvannealed steel sheet and a method for producing the same based on the above findings (Japanese Patent Application No. 2000-212591). The invention according to this application is characterized in that it has a flat portion with an area ratio of 20 to 80% on the surface of the iron-zinc alloy plating, and has an oxide layer with a thickness of 10 nm or more on the surface layer of the flat portion. An alloyed hot-dip galvanized steel sheet.In producing the steel sheet, the steel sheet is subjected to hot-dip galvanizing, further alloyed by heat treatment, subjected to temper rolling, and then brought into contact with an acidic solution to form an oxide on the plating surface layer. A method for producing an alloyed hot-dip galvanized steel sheet, comprising forming a layer.

The present inventors have further studied a method for producing an alloyed hot-dip coated steel sheet having excellent slidability during press forming. As a result, in the above-mentioned production method, the steel sheet was left for 1.0 to 30.0 seconds after the end of the contact with the acidic solution. It has been clarified that a steel sheet having excellent sliding characteristics can be manufactured more stably by washing with water and drying.

The present invention has been made based on the above findings, and the gist is as follows.

(1) The area ratio of the iron-zinc alloy plating surface is 20
It has a flat part of ~ 80%, and the surface layer of the flat part has a thickness of 10 nm.
In producing an alloyed hot-dip galvanized steel sheet having the above oxide layer, the steel sheet is subjected to hot-dip galvanizing, further alloyed by heat treatment, subjected to temper rolling, then brought into contact with an acidic solution, and after the contact is completed. After leaving for 1.0 to 30.0 seconds, wash with water,
A method for producing an alloyed hot-dip galvanized steel sheet, comprising drying.

(2) The method for producing a galvannealed steel sheet according to the above (1), wherein the steel sheet is allowed to stand for 1.0 to 30.0 seconds after the contact with the acidic solution, and then contacted with steam before washing with water and drying. Method.

(3) The method according to the above (1) or (2), wherein after the temper rolling, before the contact with the acidic solution, the surface is activated by contacting with an alkaline solution. Manufacturing method of galvannealed steel sheet.

(4) The method according to (1) to (3), wherein after the contact with the acidic solution, the amount of the acidic solution is adjusted to 3.0 g / m ² or less per one side and then left for 1.0 to 30.0 seconds. The method for producing the galvannealed steel sheet according to any one of the above.

(5) The method for producing a galvannealed steel sheet according to any one of the above (1) to (4), wherein the acidic solution is an acidic solution containing Fe and Zn ions.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION In the production of an alloyed hot-dip galvanized steel sheet, the steel sheet is subjected to hot-dip galvanizing and then further heated and alloyed. Irregularities exist on the surface of the galvannealed steel sheet due to the difference in reactivity at the plating interface. However, after the alloying treatment, temper rolling is usually performed to secure the material, and the contact with the roll at the time of the temper rolling causes the plating surface to be smoothed and unevenness is reduced. Therefore, at the time of press molding, the force required for the mold to crush the projections on the plating surface is reduced, and the sliding characteristics can be improved.

Since the flat part of the surface of the galvannealed steel sheet is a part that the mold directly contacts during press forming, the presence of a hard and high-melting substance that prevents adhesion to the mold is present. It is important for improving the slidability. In this regard, the presence of the oxide layer on the surface layer is effective in improving the sliding characteristics because the oxide layer prevents adhesion to the mold.

At the time of actual press forming, the oxide on the surface layer is worn out and scraped off. Therefore, when the contact area between the mold and the workpiece is large, it is necessary to have a sufficiently thick oxide film. Although an oxide layer is formed on the plating surface by heating during the alloying process, most of it is destroyed by contact with the roll during temper rolling, and the new surface is exposed,
In order to obtain good slidability, a thick oxide layer must be formed before temper rolling. Also, taking this into consideration, even if a thick oxide layer is formed before the temper rolling, the oxide layer at the flat portion cannot be prevented from being destroyed at the time of the temper rolling. It is not uniform, and good slidability cannot be obtained stably.

[0024] Therefore, when a treatment for uniformly forming an oxide layer on a tempered rolled alloyed hot-dip galvanized steel sheet, particularly a flat surface of a plated surface, it is possible to stably obtain good slidability. Can be.

An oxide layer can be formed on the surface of the galvanized steel sheet by bringing the galvannealed steel sheet into contact with an acidic solution. After the contact with the acidic solution, the steel sheet is allowed to stand for 1.0 to 30.0 seconds, then washed with water and dried. In addition, an oxide layer having excellent sliding characteristics can be stably formed on the flat portion of the plating surface.

Although the mechanism of formation of the oxide layer is not clear, it is left for 1.0 to 30.0 seconds after the end of the contact with the acidic solution, washed with water and dried to form a hydroxide of zinc formed by the contact with the acidic solution. It is considered that the formation reaction of the oxide is further promoted, and the oxide can be more reliably formed on the plating surface layer. If the leaving time exceeds 30.0 seconds, the effect of improving the sliding characteristics is saturated. Therefore, the leaving time is preferably 30.0 seconds or less. Here, the term "contact end" is defined as a stage at which the process of supplying the acidic solution to the plated steel sheet by a method such as immersion or spraying is completed.

If the pH of the acidic solution used in the above treatment is too low, the dissolution of zinc is promoted, but the formation of oxides is difficult, so that the pH is preferably 1 or more. On the other hand, pH
Is too high, the reaction rate of zinc dissolution will decrease,
The pH is desirably 5 or less.

Examples of the method of contacting with the acidic solution include a method of dipping the plated steel sheet in the acidic solution, a method of spraying the acidic solution on the plated steel sheet, and a method of applying the acidic solution to the plated steel sheet via a coating roll.

The acidic solution used in the above treatment is Fe
And an acidic solution containing Zn ions. Fe and
The use of a solution containing Zn ions has the effect of reducing the variation in the coefficient of friction after the oxidation treatment, and since these are components contained in the plating film, these components have an adverse effect even if they remain on the plating surface. There is no.

After the contact with the acidic solution, it is more preferable to adjust the amount of the acidic solution to be applied to 3.0 g / m ² or less per one side, and then to stand for the above-mentioned time. It is considered that the effect of promoting the reaction of generating the hydroxide of zinc in the subsequent leaving step can be improved by setting the amount of the coating in the above range.
The adhesion amount can be adjusted by a squeezing roll, air wiping, or the like.

If the acidic solution remains on the surface of the steel sheet after washing with water and drying, rust easily occurs when the steel sheet coil is stored for a long period of time. From the viewpoint of preventing the generation of rust, a treatment for neutralizing the acidic solution remaining on the surface of the steel sheet may be performed by bringing it into contact with the alkaline solution by a method such as immersion in an alkaline solution or spraying the alkaline solution. The alkaline solution preferably has a pH of 12 or less in order to prevent dissolution of the Zn-based oxide formed on the surface. The solution to be used is not limited as long as it is within the above pH range, and sodium hydroxide, sodium phosphate and the like can be used.

If the mixture is left for the above-mentioned period of time, or if it is further subjected to a neutralization treatment by contacting with an alkaline solution, it is more preferable that after the neutralization treatment, it is brought into contact with high-temperature steam before washing with water and drying. . Zinc easily forms a zinc-based oxide upon contact with a neutral solution, and the reaction proceeds rapidly in a high temperature state. By contacting with high-temperature steam, an oxide layer necessary for improving slidability can be surely formed in a short time. Here, as a method of contacting with high-temperature steam, a method of blowing steam into spray water and spraying the same onto a steel plate can be used. The conditions for spraying steam are not particularly defined, but it is preferable that the temperature is 100 ° C. or more and the spray pressure is 1 kg / mm ² or more.

It is more effective to remove the oxide layer remaining on the surface layer before forming the oxide layer by contacting with the acidic solution as described above. This is because the surface oxide is destroyed by the contact with the roll at the time of temper rolling, but a part of the surface oxide remains but the reactivity of the surface is uneven. As a method for removing the oxide layer remaining on the surface layer, a method for chemically removing the oxide layer by immersion in an alkaline solution or treatment by spraying is effective. If the alkaline solution is used, the oxide layer remaining on the surface layer can be removed and activated. However, if the pH is low, the reaction is slow and the treatment takes a long time, so that the pH is preferably 10 or more. As long as the pH is within the above range, the type of the solution is not limited, and sodium hydroxide or the like can be used.

The oxide layer according to the present invention includes Zn, Fe, Al
And one or more oxides and / or hydroxides of other metal elements.

By setting the thickness of the oxide layer in the flat portion of the plating surface layer to 10 nm or more, an alloyed hot-dip galvanized steel sheet exhibiting good slidability is obtained, but the thickness of the oxide layer is set to 20 nm or more. Is more effective. This is because, in the press forming process in which the contact area between the mold and the workpiece increases, even if the surface oxide layer is worn, the oxide layer remains and does not cause a decrease in slidability. On the other hand, the upper limit of the thickness of the oxide layer is not particularly provided, but if it exceeds 200 nm, the reactivity of the surface is extremely reduced, and it becomes difficult to form a chemical conversion treatment film. .

The thickness of the oxide layer on the surface of the flat part is Ar
It can be determined by Auger electron spectroscopy (AES) in combination with ion sputtering. In this method, after sputtering to a predetermined thickness, the composition at the depth can be obtained by correcting the relative sensitivity factor from the spectral intensity of each element to be measured. The O content due to oxides or hydroxides reaches a maximum at a certain depth (which may be the outermost layer), and then decreases and becomes constant.
At a position where the O content is deeper than the maximum value, the depth at which the sum of the maximum value and the constant value is 1/2 is defined as the oxide thickness.

Here, it is desirable that the area ratio of the flat portion on the plating surface is 20 to 80%. If it is less than 20%, the contact area with the mold in the portion (concave portion) excluding the flat portion becomes large, and the area ratio of the flat portion in which the oxide thickness can be reliably controlled in the area actually in contact with the mold. , The effect of improving press formability is reduced. In addition, the portion excluding the flat portion has a role of holding press oil at the time of press molding. Therefore, when the area ratio of the portion excluding the flat portion is less than 20% (when the area ratio of the flat portion exceeds 80%), oil shortage tends to occur during press molding, and the effect of improving press moldability is reduced.

The flat portion of the plating surface can be easily identified by observing the surface with an optical microscope or a scanning electron microscope. The area ratio of the flat portion on the plating surface can be determined by image analysis of the micrograph.

For producing the alloyed hot-dip galvanized steel sheet according to the present invention, it is necessary that Al is added to the plating bath, but the additional element components other than Al are not particularly limited. That is, in addition to Al, Pb, Sb, Si, Sn, Mg,
Even if Mn, Ni, Ti, Li, Cu, etc. are contained or added, the effects of the present invention are not impaired.

Further, since impurities are contained in the processing solution used for the oxidation treatment or the like, S, N, P, B, Cl, Na, M
Even if n, Ca, Mg, Ba, Sr, Si and the like are taken into the oxide layer, the effect of the present invention is not impaired.

[0041]

Next, the present invention will be described in more detail with reference to examples. (Example 1) An alloyed hot-dip galvanized film was formed on a cold-rolled steel sheet having a thickness of 0.8 mm by a normal method, and further temper rolling was performed. At this time, the flat portion area ratio on the surface was adjusted to a range of 20 to 80% by changing the rolling load of the temper rolling. Subsequently, an oxide layer was formed using the processing equipment having the configuration shown in FIG.

That is, after the immersion treatment was performed in a sulfuric acid solution adjusted to 50 ° C. and pH 1.5 in the acid solution tank 2, the amount of the acid solution adhered to the steel sheet surface was adjusted by the squeezing roll 3. Next, the steel plate is sprayed with 50 ° C hot water in the # 1 washing tank 5, the neutralization tank 6 is passed through, the 50 ° C hot water is sprayed on the steel sheet in the # 2 washing tank 7, and washed, and the dryer 8 is dried. Then, an oxide layer was formed on the plating surface.

With respect to some steel sheets, the steel sheets are washed immediately after squeezing using the shower rinsing device 4 on the exit side of the squeezing roll 3 during the above-mentioned treatment, and / or an alkaline treatment liquid (pH 10) in the neutralization tank 6. An aqueous solution of sodium hydroxide was sprayed to neutralize the acidic solution remaining on the steel sheet surface.

Table 1 shows the processing conditions. In Table 1, the standing time is the time from when the amount of the acidic solution adhered to the steel sheet surface is adjusted by the squeezing roll 3 to when the washing is started with the # 1 washing tank 5 or the shower device 4.

Next, regarding the steel sheet manufactured as described above,
The measurement of the Fe concentration in the plating film, the area ratio of the flat portion, the thickness of the oxide layer, and the press formability test were performed. Also, after applying rust preventive oil to the steel sheet, leave it outdoors so that there is no influence of external factors such as dust, and investigate the occurrence of rust spots after about 6 months. The presence of spot rust was evaluated as “×”.
The measurement of the thickness of the oxide layer on the flat portion and the press formability test were performed as follows.

(1) Oxide Layer Thickness Measurement The content (at%) of each element in the flat portion was measured by Auger electron spectroscopy (AES), followed by Ar sputtering to a predetermined depth, followed by AES The content of each element in the plating film was measured, and by repeating this, the composition distribution of each element in the depth direction was measured. After the content of O due to oxides and hydroxides reaches a maximum at a certain depth,
Decreases and becomes constant. The depth at which the O content was half of the sum of the maximum value and the constant value at a position deeper than the maximum value was defined as the oxide thickness. The thickness of the oxide on the flat portion at a plurality of arbitrarily selected portions (n = 3) was measured, and the average value was determined. Note that, as a preliminary treatment, Ar sputtering was performed for 30 seconds to remove the contamination layer on the surface of the test material.

(2) Evaluation Test of Press Formability (Test for Measuring Friction Coefficient) In order to evaluate the press formability, the friction coefficient of each test material was measured as follows.

FIG. 2 is a schematic front view showing a friction coefficient measuring device. As shown in the figure, a friction coefficient measurement sample 11 collected from a test material is fixed to a sample table 12, and the sample table 12 is
It is fixed to the upper surface of a horizontally movable slide table 13. On the lower surface of the slide table 13, a vertically movable slide table support 15 having a roller 14 in contact therewith is provided.
A first load cell 17 for measuring a pressing load N of the bead 16 against the friction coefficient measurement sample 11 by being pushed up is attached to the slide table support 15. A sliding resistance force for moving the slide table 13 in the horizontal direction while the pressing force is applied.
A second load cell 18 for measuring F is attached to one end of the slide table 13. As a lubricating oil, Noxlast 550HN manufactured by Nippon Parkerizing Co., Ltd.
Was applied to the surface of Sample 11 to perform a test.

FIGS. 3 and 4 are schematic perspective views showing the shapes and dimensions of the beads used. The bead 16 slides while being pressed against the surface of the sample 11. The shape of the bead 16 shown in FIG. 3 is 10 mm in width, the length in the sliding direction of the sample is 12 mm, the lower part of both ends in the sliding direction is a curved surface with a curvature of 4.5 mmR, the lower surface of the bead on which the sample is pressed is 10 mm in width, the sliding direction It has a plane with a length of 3 mm. The shape of the bead 16 shown in FIG. 4 is 10 mm in width, the length of the sample in the sliding direction is 69 mm, and the lower part at both ends in the sliding direction is a curved surface with a curvature of 4.5 mmR.
mm, and has a plane with a length of 60 mm in the sliding direction.

The friction coefficient measurement test was performed under the following two conditions. (Condition 1) Using the bead shown in Fig. 3, pressing force N: 400
kgf, sample withdrawal speed (horizontal movement speed of slide table 13): 100 cm / min. (Condition 2) Using the bead shown in Fig. 4, pressing force N: 400
kgf, sample withdrawal speed (horizontal movement speed of slide table 13): 20 cm / min. The friction coefficient μ between the test material and the bead was calculated by the formula: μ = F / N. Table 1 shows test results
Shown in

[0051]

【table 1】

From the test results in Table 1, the following matters are clear. (1) No. 1 (Comparative Example) is an example of an alloyed hot-dip galvanized steel sheet that has not been subjected to temper rolling, and has a high coefficient of friction. (2) No. 2 and No. 3 (comparative examples) had no oxide forming treatment after temper rolling, so the oxide thickness was 10 nm.
Less and less, high coefficient of friction. (3) No. 4 and No. 5 (Comparative Examples) were treated with an acidic solution after temper rolling, but the standing time was shorter than within the range of the present invention, and the thickness of the oxide in the flat portion was smaller. Is less than 10 nm, the effect of improving the coefficient of friction is hardly obtained.

(4) No. 6 to No. 11 are acidic solutions after temper rolling.
Immersion, and further, because the leaving time is within the scope of the present invention,
Oxide thickness is more than 10nm, coefficient of friction is improved
Have been. Furthermore, immerse in an acidic solution and squeeze roll
The adjusted adhesion amount is 3.0g / m^TwoIf it is below (No.12 ~ No.2
3) shows that the adhesion amount is 3.0g / m ^TwoTo
The oxide thickness is larger than the
Good effect is great.

(5) No. 18 to No. 23 are examples in which a neutralization treatment was performed by spraying an alkaline treatment liquid on the steel sheet after the treatment. In this case, by performing the neutralization treatment, there is no rust at all after being left outdoors for a long time, and even if the steel sheet coil with the oxide layer is stored for a long time before use, rust generation is prevented. Excellent ability to do.

(Example 2) An alloyed hot-dip galvanized film was formed on a cold-rolled steel sheet having a thickness of 0.8 mm by a conventional method, followed by temper rolling. At this time, the flat portion area ratio on the surface was adjusted to a range of 20 to 80% by changing the rolling load of the temper rolling. Subsequently, an oxide layer was formed using the processing equipment having the configuration shown in FIG.

That is, the immersion treatment was performed in a sulfuric acid solution adjusted to 50 ° C. and pH 1.5 in the acid solution tank 2, and the amount of the acid solution adhered to the steel sheet surface was adjusted by the squeezing roll 3. Then, hot water of 50 ° C. is sprayed on the steel sheet in # 1 washing tank 5, air is passed through neutralizing tank 6, and steam of 100 ° C. in which steam is previously blown into the hot water in # 2 washing tank 7 is sprayed at a pressure of 1 kg / kg. After spraying the steel sheet with mm ^2, it was dried with a dryer 8 to form an oxide layer on the plating surface.

For some steel sheets, the steel sheets are washed immediately after squeezing using the shower rinsing device 4 on the exit side of the squeezing roll 3 during the above treatment, and / or an alkaline treatment liquid (pH 10) in the neutralization tank 6. (Aqueous sodium hydroxide solution) to neutralize with the acidic solution remaining on the steel sheet surface, and / or 5
Hot water at 0 ° C. was sprayed on the steel sheet.

Table 2 shows the processing conditions. In Table 2, the standing time is the time from the adjustment of the amount of the acidic solution adhered to the steel sheet surface by the squeezing roll 3 to the start of cleaning in the # 1 cleaning tank 5 or the shower water washing device 4.

Next, the specimens prepared as described above were subjected to the measurement of the Fe concentration in the plating film, the area ratio of the flat portion, the thickness of the oxide layer, and the press formability test in the same manner as in Example 1. In addition, after applying rust-preventive oil to the steel sheet, it was left outdoors so as not to be affected by external factors such as dust, and the occurrence of rust spot after about 6 months was investigated. Table 2 shows the test results.

[0060]

[Table 2]

From the test results in Table 2, the following matters are clear. (1) No. 1 (Comparative Example) is an example of an alloyed hot-dip galvanized steel sheet that has not been subjected to temper rolling, and has a high coefficient of friction. (2) No. 2 and No. 3 (comparative examples) had no oxide forming treatment after temper rolling, so the oxide thickness was 10 nm.
Less and less, high coefficient of friction.

(3) For No. 12 to No. 29, the standing time after immersion in the acidic solution was within the range of the present invention, and furthermore, since the steam spraying treatment was performed, the friction coefficient was improved for all. I have. Furthermore, when immersed in an acidic solution and the adhesion amount adjusted with a squeeze roll is 3.0 g / m ² or less (No. 18 to No. 2
In 9), when compared with the same standing time, the thickness of the oxide is larger and the effect of improving the coefficient of friction is greater than in the case where the adhesion amount exceeds 3.0 g / m ² . On the other hand, when the standing time after immersion in the acidic solution is not included in the range of the present invention (No. 10, N
o.11) indicates that although the effect of improving the friction coefficient is
The improvement effect is small compared to No. 12 to No. 29.

Nos. 12 to 29 were immersed in an acidic solution and allowed to stand still within the scope of the present invention, but were not subjected to steam treatment (Nos. 4 to 9). Thus, the effect of improving the coefficient of friction is greater.

(4) Nos. 24 to 29 are examples in which a neutralization treatment was performed by spraying an alkaline treatment liquid on the steel sheet after the treatment. In this case, by performing the neutralization treatment, there is no rust at all after being left outdoors for a long time, and even if the steel sheet coil with the oxide layer is stored for a long time before use, rust generation is prevented. Excellent ability to do.

Example 3 An ordinary galvannealed film was formed on a cold-rolled steel sheet having a thickness of 0.8 mm, and temper rolling was further performed. At this time, the flat portion area ratio on the surface was adjusted to a range of 20 to 80% by changing the rolling load of the temper rolling. Subsequently, an oxide layer was formed using the processing equipment having the configuration shown in FIG.

That is, after the immersion treatment was performed in a sulfuric acid solution adjusted to 50 ° C. and pH 1.5 in the acid solution tank 2, the amount of the acid solution adhered to the steel sheet surface was adjusted by the squeezing roll 3. Next, the steel plate is sprayed with 50 ° C hot water in the # 1 washing tank 5, the neutralization tank 6 is passed through, the 50 ° C hot water is sprayed on the steel sheet in the # 2 washing tank 7, and washed, and the dryer 8 is dried. Then, an oxide layer was formed on the plating surface.

For some steel sheets, during the above treatment,
A treatment for washing the steel sheet immediately after squeezing using the shower rinsing device 4 on the exit side of the squeezing roll 3, a treatment using an alkaline solution in the activation tank 1 before the immersion treatment in the acidic solution, and a neutralization tank 6 At least one of neutralization treatments in which an alkaline treatment solution (aqueous sodium hydroxide solution) having a pH of 10 is sprayed.

Table 3 shows the processing conditions. In Table 3, the standing time is the time from the adjustment of the amount of the acidic solution adhering to the steel sheet surface by the squeezing roll 3 to the start of washing in the # 1 washing tank 6 or the shower water washing device 4.

Next, in the same manner as in Example 1, measurement of the Fe concentration in the plating film, the area ratio of the flat portion, the thickness of the oxide layer, and the press formability test were performed on the specimens prepared as described above. In addition, after applying rust-preventive oil to the steel sheet, it was left outdoors so as not to be affected by external factors such as dust, and the occurrence of rust spot after about 6 months was investigated. Table 3 shows the test results.

[0070]

[Table 3]

From the test results in Table 3, the following matters are clear. (1) No. 1 (Comparative Example) is an example of an alloyed hot-dip galvanized steel sheet that has not been subjected to temper rolling, and has a high coefficient of friction. (2) No. 2 and No. 3 (comparative examples) had no oxide forming treatment after temper rolling, so the oxide thickness was 10 nm.
Less and less, high coefficient of friction.

(3) For No. 12 to No. 29, the activation treatment was performed after temper rolling, and the standing time after immersion in an acidic solution was within the range of the present invention. Have been. Furthermore, when immersed in an acidic solution and the adhesion amount adjusted with a squeezing roll is 3.0 g / m ² or less (No. 18 to No. 29)
When compared with the same standing time, the oxide thickness is larger and the effect of improving the friction coefficient is greater than when the adhesion amount exceeds 3.0 g / m ² . On the other hand, when the standing time after immersion in the acidic solution is not included in the range of the present invention (No. 10, No.
11) shows that the above-mentioned N
The improvement effect is small compared to o.12 to No.29.

Nos. 12 to 29 were immersed in an acidic solution and allowed to stand still within the scope of the present invention, but were not activated (Nos. 4 to 9). In comparison, the effect of improving the coefficient of friction is greater.

(4) Nos. 24 to 29 are examples in which a neutralization treatment was performed by spraying an alkaline treatment solution onto the steel sheet after the treatment. In this case, by performing the neutralization treatment, there is no rust at all after being left outdoors for a long time, and even if the steel sheet coil with the oxide layer is stored for a long time before use, rust generation is prevented. Excellent ability to do.

(Example 4) An alloyed hot-dip galvanized film was formed on a cold-rolled steel sheet having a thickness of 0.8 mm by a conventional method, followed by temper rolling. At this time, the flat portion area ratio on the surface was adjusted to a range of 20 to 80% by changing the rolling load of the temper rolling. Subsequently, an oxide layer was formed using the processing equipment having the configuration shown in FIG.

That is, after immersion treatment was performed in a sulfuric acid solution adjusted to 50 ° C. and pH 1.5 in the acid solution tank 2, the amount of the acid solution adhered to the steel sheet surface was adjusted by the squeezing roll 3. Next, the steel plate is sprayed with 50 ° C hot water in the # 1 washing tank 5, the neutralization tank 6 is passed through, the 50 ° C hot water is sprayed on the steel sheet in the # 2 washing tank 7, and washed, and the dryer 8 is dried. Then, an oxide layer was formed on the plating surface.

Some of the steel sheets were treated with an alkaline solution in the activation tank 1 before the immersion treatment in the acidic solution. For some steel sheets, during the above process,
A treatment for washing the steel sheet immediately after squeezing using the shower water washing device 4 on the exit side of the squeezing roll 3, and spraying an alkaline treatment liquid (aqueous sodium hydroxide solution) having a pH of 10 in the neutralization tank 6 to remove the acid remaining on the steel sheet surface. In the neutralization treatment of the solution, in the # 2 washing tank, steam was previously blown into hot water instead of hot water spray
At least one of the treatments of spraying steam at 100 ° C. on the steel sheet at a pressure of 1 kg / mm ² was performed.

Tables 4 and 5 show the processing conditions. In Tables 4 and 5, the leaving time is the time from when the amount of the acidic solution adhered to the steel sheet surface is adjusted by the squeezing roll 3 to when the washing is started in the # 1 washing tank 6 or the shower water washing device 4.

Next, the specimens prepared as described above were subjected to the measurement of the Fe concentration in the plating film, the area ratio of the flat portion, the thickness of the oxide layer, and the press formability test in the same manner as in Example 1. In addition, after applying rust-preventive oil to the steel sheet, it was left outdoors so as not to be affected by external factors such as dust, and the occurrence of rust spot after about 6 months was investigated. The test results are shown in Tables 4 and 5.

[0080]

[Table 4]

[0081]

[Table 5]

From the test results in Tables 4 and 5, the following matters are clear. (1) No. 1 (Comparative Example) is an example of an alloyed hot-dip galvanized steel sheet that has not been subjected to temper rolling, and has a high coefficient of friction. (2) No. 2 and No. 3 (comparative examples) had no oxide forming treatment after temper rolling, so the oxide thickness was 10 nm.
Less and less, high coefficient of friction.

(3) No. 24 to No. 41 were subjected to an activation treatment after temper rolling, and a standing time after immersion in an acidic solution was within the range of the present invention. In each case, the coefficient of friction is improved.
Furthermore, when the adhesion amount adjusted by a squeezing roll after immersion in an acidic solution is 3.0 g / m ² or less (No. 30 to No. 41), the adhesion amount is 3.0 g / m ² when compared with the same standing time. The thickness of the oxide is larger and the effect of improving the coefficient of friction is larger than in the case of exceeding ² . On the other hand, when the standing time after immersion in the acidic solution is not included in the range of the present invention (No. 22, No. 23),
Although the effect of improving the coefficient of friction is seen, the above No. 24 to No.
The improvement effect is small compared to 41.

Nos. 24 to 41 were immersed in an acidic solution and allowed to stand still within the scope of the present invention, but neither the activation treatment nor the steam spraying treatment was performed (No. 4). To No. 9) and when only one of them is applied (No. 10 to No. 22), the effect of improving the friction coefficient is larger.

(4) Nos. 36 to 41 are examples in which a neutralization treatment was performed by spraying an alkaline treatment liquid onto a steel sheet after treatment. In this case, by performing the neutralization treatment, there is no rust at all after being left outdoors for a long time, and even if the steel sheet coil with the oxide layer is stored for a long time before use, rust generation is prevented. Excellent ability to do.

[0086]

According to the present invention, a galvannealed steel sheet having low sliding resistance during press forming and exhibiting excellent press formability stably can be manufactured.

[Brief description of the drawings]

FIG. 1 is a view showing a main part of an oxide layer forming treatment facility used in Examples 1 and 2.

FIG. 2 is a schematic front view showing a friction coefficient measuring device.

FIG. 3 is a schematic perspective view showing a bead shape and dimensions in FIG. 2;

FIG. 4 is a schematic perspective view showing another bead shape and dimensions in FIG. 2;

FIG. 5 is a diagram illustrating a main part of an oxide layer forming treatment facility used in Examples 3 and 4.

[Explanation of symbols]

 1 Activation tank 2 Acid solution tank 3 Squeeze roll 4 Shower water washing device 5 # 1 Wash tank 6 Neutralization tank 7 # 2 Wash tank 8 Dryer 11 Sample for friction coefficient measurement 12 Sample table 13 Slide table 14 Roller 15 Slide table support 16 Bead 17 First load cell 18 Second load cell 19 Rail S Steel plate N Pressing load F Sliding resistance P Tensile load

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 22/83 C23C 22/83 28/00 28/00 C (72) Inventor Toshisaku Node Chiyoda-ku, Tokyo 1-2-1 Marunouchi Nihon Kokan Co., Ltd. (72) Inventor Masahiro Iwabuchi 1-1-2 Marunouchi Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. 1-2-1, Nihon Kokan Co., Ltd. (72) Inventor, Yukiki Osaki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor, Shinichi Asanaga 1-2-1 Nihon Kokan Co., Ltd. (72) Inventor Shoichiro Hira 1-1-2 Marunouchi Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Yoshiharu Sugimoto Tokyo 1-1-2 Marunouchi, Chiyoda-ku Nihon Kokan Co., Ltd. F-term (reference) 4K026 AA02 AA07 AA13 AA22 BA08 BB04 BB09 CA13 CA18 CA33 CA36 DA03 DA11 DA12 DA15 EA01 EA03 EA07 EA10 EB01 4K027 AA02 AC02 AB42 AC AC87 AE21 AE27 4K044 AA02 AB02 BA10 BA12 BB03 BC01 BC05 CA07 CA11 CA16 CA53

Claims (5)

[Claims] Claims 1. An iron-zinc alloy plating surface has an area ratio of 20 to 8
When manufacturing an alloyed hot-dip galvanized steel sheet having a flat portion of 0% and an oxide layer having a thickness of 10 nm or more on the surface layer of the flat portion, the steel sheet is subjected to hot-dip galvanizing, and further subjected to heat treatment. A method for producing an alloyed hot-dip galvanized steel sheet, comprising subjecting the steel to contact with an acidic solution, subjecting to temper rolling, leaving the contact for 1.0 to 30.0 seconds after completion of the contact, washing with water, and drying. 2. The method for producing an alloyed hot-dip galvanized steel sheet according to claim 1, wherein the steel sheet is allowed to stand for 1.0 to 30.0 seconds after contact with the acidic solution, and then contacted with steam before being washed with water and dried. 3. The alloyed molten zinc according to claim 1 or 2, wherein the surface activation treatment is performed by contacting with an alkaline solution before the contact with the acidic solution after the temper rolling. Manufacturing method of plated steel sheet. 4. The method according to claim 1, wherein after the contact with the acidic solution, the adhesion amount of the acidic solution is adjusted to 3.0 g / m ² or less per one side, and then left for 1.0 to 30.0 seconds. Of manufacturing galvannealed steel sheet. 5. The method for producing a galvannealed steel sheet according to claim 1, wherein the acidic solution is an acidic solution containing Fe and Zn ions.