JP3111888B2 - Manufacturing method of galvanized steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a press formability,
The present invention relates to a method for producing a galvanized steel sheet having excellent spot weldability and adhesiveness.

[0002]

2. Description of the Related Art Galvanized steel sheets are widely used as various kinds of rust-proof steel sheets because they have various excellent characteristics. In order to use this galvanized steel sheet as an anti-corrosion steel sheet for automobiles, in addition to corrosion resistance, paint compatibility, etc., it is required to have excellent press formability, spot weldability and adhesion as the performance required in the body manufacturing process. It is important that

[0003] However, galvanized steel sheets generally have a drawback that press formability is inferior to cold-rolled steel sheets. This is because the sliding resistance between the galvanized steel sheet and the press die is greater than that of the cold-rolled steel sheet. The galvanized steel sheet hardly flows into the press die, and the steel sheet is easily broken.

[0004] As a method for improving the press formability of a zinc-based plated steel sheet, a method of applying a high-viscosity lubricating oil is generally widely used. However, in this method, since the lubricating oil has a high viscosity, there is a problem that a coating defect occurs due to poor degreasing in the next coating process, and there is a problem that press performance becomes unstable due to lack of oil, etc. There is a high demand for improved press formability of galvanized steel sheets.

On the other hand, in a zinc-based plated steel sheet, copper, which is an electrode, and molten zinc easily react during spot welding to form a brittle alloy layer. Therefore, the copper electrode is severely worn and its life is short. There is a problem that continuous hitting properties are inferior to cold-rolled steel sheets.

Further, in the manufacturing process of an automobile body,
Various adhesives are used for the purpose of rust prevention and vibration damping, etc., but it has recently become clear that galvanized steel sheets are inferior in adhesiveness to cold rolled steel sheets.

As a method for solving the above problem, Japanese Patent Laid-Open No.
Japanese Patent Application Laid-Open No. 190483/1999 improves the weldability or workability by subjecting the surface of a galvanized steel sheet to electrolytic treatment, immersion treatment, coating oxidation treatment, or heat treatment to generate an oxide film mainly composed of ZnO. (Hereinafter referred to as "prior art 1").

[0008] JP-A-3-17282 discloses that Fe, N
A method of substituting and precipitating one or more selected from i and Co on the surface of a galvanized steel sheet (hereinafter, referred to as i and Co).
"Prior art 2" is disclosed in
Japanese Patent Application Laid-Open No. 91093 discloses a technique (hereinafter, referred to as "prior art 3") for improving press formability and chemical conversion property by generating Ni oxide.
No. 94 discloses a method of applying an aqueous solution of an inert film component (hereinafter referred to as “prior art 4”).

Japanese Patent Application Laid-Open No. Hei 4-21751 discloses that a galvanized steel sheet containing Al in a plating layer contains an oxidizing agent having an oxidizing power for Zn metal and has a pH of 1 or more.
A method of contacting with an alkali solution having a temperature of 40 ° C. or higher at one or more temperatures (hereinafter referred to as “prior art document 5”) is disclosed.

[0010]

The prior art 1 described above has the following problems. That is, prior art 1
In this method, an oxide mainly composed of ZnO is generated on the surface of the plating layer by various treatments, so that the effect of reducing the sliding resistance between the press die and the plated steel sheet is small, and the effect of improving the press formability is reduced. Is small. Further, an oxide mainly composed of ZnO deteriorates adhesiveness.

Prior art 2 has the following problems. In the method of depositing metals such as Ni and Fe, corrosion resistance is improved, but sufficient adhesion cannot be obtained because the wettability of the metal to the adhesive is small. In addition, since the metallic properties of the film are strong, there is a problem that the effect of improving press formability and spot weldability is small. Further, since the pH of the aqueous solution is low and the displacement precipitation efficiency is low, it is not possible to secure a sufficient amount of deposition, and it is necessary to increase the temperature of the aqueous solution to secure the amount of deposition, and the However, there is a problem that the production cost is increased, for example, the production cost is increased or an aqueous solution heating facility is provided.

Here, the term "spot weldability" as used herein refers to the continuous spotting property in spot welding of thin steel sheets, and the number of times that spot welding can be performed continuously without care or replacement of the welding electrode tip. And is consistent with the electrode life that can be used continuously.

Prior Art 3 is a single-phase Ni oxide film, so that press formability is improved, but there is a problem that adhesion is deteriorated. Prior Art 4 is a method of forming an inert film, and thus has a problem that chemical conversion property and adhesiveness are deteriorated.

The prior art 5 is a method for forming an oxide film mainly composed of a hydroxide and an oxide of Zn not containing Al on a galvanized steel sheet containing Al in the plating layer. As in the technology 1, the effect of reducing the sliding resistance between the press die and the plated steel sheet is small, and the effect of improving the press formability is small.

Accordingly, it is an object of the present invention to solve the above-mentioned problems and to provide a method for producing a galvanized steel sheet which is particularly excellent in press formability and also excellent in spot weldability and adhesiveness. is there.

[0016]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have obtained the following findings.

On the surface of the plating layer of the zinc-based plated steel sheet, F
forming an e-Ni-O-based film, and Fe-N
Improving press formability, spot weldability and adhesion by subjecting a zinc-based plated steel sheet to an alkali treatment and then temper rolling immediately before forming an i-O-based coating, or a temper rolling and then alkali treatment. I found that I could do it.

The reason why the press formability of a zinc-based plated steel sheet is inferior to that of a cold-rolled steel sheet is that, under high surface pressure, the low melting point zinc and the mold cause an adhesion phenomenon, so that the sliding resistance is low. It is because it increases. In order to prevent this, it is effective to form a harder and higher-melting film than the zinc or zinc alloy plating layer on the surface of the plating layer of the zinc-based plated steel sheet, and thus the plating layer surface during press molding is effective. The sliding resistance with the press mold is reduced, and the zinc-based plated steel sheet easily slides into the press mold, and the press formability is improved.

The reason why the continuous spotting property in spot welding of a zinc-based plated steel sheet is inferior to that of a cold-rolled steel sheet is that the molten zinc contacts the copper of the electrode at the time of welding to form a brittle alloy layer on the electrode surface. The reason for this is that the generation of the electrode causes severe deterioration of the electrode. As a method for improving the continuous hitting property of a zinc-based plated steel sheet, it is effective to form a high melting point film on the plating surface. The present inventors have studied various coatings in order to improve the spot weldability of galvanized steel sheets, and as a result, have found that an Fe-Ni-O-based coating is particularly effective. Although the details of this reason are not clear, Ni reacts with Zn to form a high-melting Zn-Ni alloy, Ni oxide has a very high melting point,
Further, it is considered that the reason for this is that it has high electrical conductivity due to its semiconductor properties.

It has been known that the galvanized steel sheet has inferior adhesiveness to that of the cold-rolled steel sheet, but the cause has not been clarified. The present inventors have investigated the cause and found that the adhesiveness is governed by the composition of the oxide film on the surface of the steel sheet. That is,
In the case of a cold-rolled steel sheet, the oxide film on the surface of the steel sheet is mainly composed of Fe oxide, while the zinc-coated steel sheet has a Zn oxide coating.
Oxides mainly. The adhesiveness differs depending on the composition of the oxide film, and the Zn oxide was inferior in adhesiveness to the Fe oxide.

Therefore, it is possible to improve the adhesiveness by forming an Fe oxide on the surface of a galvanized steel sheet as in the present invention.

The present invention has been made based on the above findings, and the method for producing a galvanized steel sheet according to claim 1 has an elongation ratio of 0.3 to the galvanized steel sheet.
Temper rolling in the range of ~ 5.0%, subjecting the tempered rolled zinc-based plated steel sheet to alkali treatment with an alkaline solution having a pH of 10 or more for 2 to 30 seconds, and then subjecting the alkali-treated zinc-based steel sheet to Fe-N on the plating layer surface of the plated steel sheet
It is characterized by forming an i-O-based film.

According to a second aspect of the present invention, there is provided a method for producing a galvanized steel sheet, wherein the galvanized steel sheet is subjected to an alkali treatment with an alkali solution having a pH of 10 or more for 2 to 30 seconds. 0.3%
Temper rolling in the range of 5.0% is performed, and then the Fe-Ni-
It is characterized by forming an O-based film.

According to a third aspect of the present invention, there is provided a method for producing a galvanized steel sheet, comprising the steps of:
As a method of the i-O-based film forming treatment, FeCl ₂ and NiCl ₂ are contained, the pH is 2.0 to 3.5, and the temperature is 2
It is characterized in that a zinc-based plated steel sheet is treated with an aqueous solution at 0 to 70 ° C.

According to a fourth aspect of the present invention, there is provided a method for producing a galvanized steel sheet, comprising the steps of:
As a method of forming the i-O-based film, the Fe content (wt.%) with respect to the sum of the Fe content (wt.%) and the Ni content (wt.%) containing FeCl ₂ and NiCl ₂ is used. The ratio is 0.004-0.9, the pH is 2.0-3.5, and the temperature is 2
It is characterized in that a zinc-based plated steel sheet is treated with an aqueous solution at 0 to 70 ° C.

In this application, the upper layer of Fe formed on the surface of the plating layer of the zinc-based plated steel sheet was used.
When referring to a -Ni-O-based film, it is referred to as a "film".
When referring to the zinc-based plating layer as the lower layer, it is referred to as “plating layer” and not as “coating”.

[0027]

Next, the reason for limiting the manufacturing conditions of the present invention as described above will be described. In the present invention, forming the Fe-Ni-O-based coating on the surface of the zinc-based plated steel sheet after treating the zinc-based plated steel sheet with an alkaline solution having a pH of 10 or more for 2 to 30 seconds is performed by changing the zinc-based plated steel sheet to an alkaline solution. This is because, in comparison with the case where the Fe—Ni—O-based film is formed without being treated with the solution, the case where the above alkali treatment is performed is remarkably excellent in press formability. Before or after treatment with an alkaline solution,
When the Fe—Ni—O-based film is formed after performing the temper rolling in the range of the elongation of 0.3% to 0.5%, the surface of the galvanized steel sheet is smoothened by the temper rolling, Fe
This is because an oxide film or the like that hinders the adhesion of the -Ni-O-based coating is removed, so that a zinc-based plated steel sheet having improved adhesion and excellent press formability can be obtained.

FIG. 1 is a graph showing the relationship between the amount of Ni deposited on the plating layer surface and the friction coefficient of a zinc-based plated steel sheet in the case of alkali solution treatment and temper rolling and in the case of no treatment. is there. From the figure, when the alkali solution treatment and the temper rolling were performed, the value of the friction coefficient in the case of the same Ni adhesion amount was smaller than that in the case where the treatment was not performed, and the press formability was excellent. You can see that it is. Here, the alkaline solution is NaOH, KOH,
Na ₂ SO ₄ , Na ₂ PO ₄ , LiOH and MgOH
One or two or more aqueous solutions of alkali chemicals such as those described above can be used. Further, the alkali concentration of the aqueous solution needs to have a pH of 10 or more.
It is more desirable to adjust H to be 11 or more. In this case, the concentration may be generally about 5 to 50 g / l.

On the other hand, when a zinc-plated steel sheet is treated with an acidic solution to form an Fe—Ni—O-based coating, although the press formability is slightly improved,
Press formability, spot weldability and adhesion are inferior to those treated with an alkali solution. This is due to the fact that by treating a zinc-based plated steel sheet with an alkaline solution, the adhesion of a subsequently formed Fe-Ni-O-based coating is improved, and the acidic solution inevitably adheres to the surface of the zinc-based plated steel sheet. It is considered that the above effect cannot be obtained because the amount of the oxide film generated in the step increases.

Here, the Fe—Ni—O-based film is a mixture of Fe metal, Fe oxide, Ni metal and Ni oxide, and the method of forming the film is not particularly limited. The treatment may be performed with an aqueous solution containing ions, nickel ions, an oxidizing agent, and the like, and may be performed by an immersion method in an aqueous solution, a spraying method and a coating method of the aqueous solution, an electroplating method, or the like. In addition, a vapor phase plating method such as laser CVD, optical CVD, vacuum vapor deposition, and sputter vapor deposition can be employed.

Further, in the above-mentioned aqueous solution for forming a film, Zn, Co, Mn, Mo, and A contained in the plating layer of the zinc-based plated steel sheet used in the present invention are inevitably contained.
It may contain cations such as 1, Ti, Sn, W, Si, Pb, Nb, and Ta, hydroxides and oxides, and further, anions.

Further, a surfactant or the like may be added to the above alkaline solution in order to enhance the alkali treatment property of the galvanized steel sheet. However, when an oxidizing agent or the like is added, an oxide is formed on the surface of the zinc-based plated steel sheet, so that the adhesion of the Fe—Ni—O-based coating deteriorates, which is not desirable.

Next, the order of the temper rolling and the alkali treatment performed before the formation of the Fe—Ni—O-based film is not limited by the order in which the adhesion amount of the Fe—Ni—O-based film is hindered. If removed, a similar effect can be obtained. Therefore, an effective order for removing the obstructive factors may be appropriately selected depending on the type of the zinc-based plated steel sheet. In addition, as for the elongation rate of the temper rolling, it is sufficient that a factor that hinders the adhesion of the Fe—Ni—O-based coating is removed, and for that purpose, 0.3 to 5.0%.
Is sufficient, but if the elongation is the same, the greater the rolling load, the greater the effect. 0.3 elongation
%, The smoothing effect is small and satisfactory press formability cannot be obtained. On the other hand, when the elongation rate exceeds 5.0%,
This is undesirable because the material deteriorates.

In the third and fourth aspects, Fe—Ni—
FeCl ₂ and NiC to form an O-based film
The reason why the aqueous solution containing l ₂ is used is that when a metal salt of chloride is used to supply the ferric ion and the nickel ion, the precipitation efficiency is high and the productivity can be improved. . In the case of the same salt concentration and processing time, Ni and Fe are compared with nitrates and sulfates.
Increases the amount of adherence.

FIG. 2 is a graph showing the relationship between the type of treatment bath for forming an Fe—Ni—O-based film and the amount of the applied film.
This is because the concentration ratio between Ni and Fe in each treatment bath is 90: 1.
At 0, the sum of the concentrations is 100 g / l in the case of a stationary bath, and it can be seen that the chloride bath is more efficient than the sulfuric acid bath and the nitric acid bath.

Further, the pH of the aqueous solution for forming the film is adjusted to 2.0 to
It is desirable to be within the range of 3.5. The reason is as follows. If the pH is less than 2.0, the amount of hydrogen generated from the cathode becomes extremely large, and the deposition efficiency becomes low. At the same salt concentration and processing time, the amount of Ni and Fe attached is small, and the productivity is reduced. is there. Further, the film is mainly composed of Ni and Fe metals, and the effect of improving press formability, spot weldability and adhesiveness cannot be obtained. On the other hand, pH
If it exceeds 3.5, the oxidation of Fe in the aqueous solution will be severe, and defects on the steel sheet surface due to sludge will occur.

FIG. 3 is a graph showing an example of the amount of Ni deposition with respect to the immersion time when the pH was changed from 2.0 to 3.5. This is because the processing bath temperature is 50 ° C., the concentration ratio between Ni and Fe in the processing bath is 20:80, and the sum of the concentrations is 100%.
g / l, and it can be seen that the higher the pH, the better the deposition efficiency.

The temperature of the aqueous solution for forming a film is from 20 to 70 ° C.
Is desirably within the range. The reason is as follows. If the temperature of the aqueous solution is lower than 20 ° C., the reaction rate is low, and a large amount of time is required to secure the adhesion amounts of Ni and Fe necessary for improving the properties of the film, thereby lowering productivity. On the other hand, when the temperature of the aqueous solution exceeds 70 ° C., the performance of the aqueous solution deteriorates rapidly, and equipment and thermal energy for maintaining the aqueous solution at a high temperature are required, resulting in an increase in manufacturing cost.

According to Claims 3 and 4, Fe-Ni-
As the solution for forming the O-based film, the Fe content (w
t. %) And the Ni content (wt.%)
Content (wt.%) Ratio (hereinafter Fe ratio: Fe /
(Referred to as (Fe + Ni)) is limited within the range of 0.004 to 0.9. When the ratio is less than 0.004, there is no effect of improving the adhesiveness. This is because the improvement effect is reduced.

The zinc-plated steel sheet used in the present invention may be any steel sheet having a zinc-based plating layer formed on the surface of the steel sheet by a hot-dip plating method, an electroplating method, a vapor phase plating method or the like. The composition of the plating layer on the surface of this galvanized steel sheet is, in addition to pure zinc, Fe, Ni, Co,
Mn, Cr, Al, Mo, Ti, Si, W, Sn, P
a metal such as b, Nb, and Ta (however, Si is also treated as a metal) or an oxide;
It may consist of a single or multiple plating layers containing more than one species. Further, SiO ₂ and Al ₂ O are formed on the plating layer.
Fine particles such as ₃ may be contained. Further, as the zinc-based plated steel sheet, a multi-layer plated steel sheet having a different composition of a plating layer and a functionally graded plated steel sheet can be used.

The Fe—Ni—O coating formed on the surface of the plating layer of the zinc-coated steel sheet under the above-described conditions eliminates the adhesion phenomenon between the steel sheet and the mold during press forming, and reduces the sliding resistance. It becomes smaller, the sliding into the mold becomes better, the formation of a brittle alloy layer between the electrode copper and the electrode during spot welding is suppressed, and the continuous hitting property is improved.
The effect of the adhesiveness being improved by the action of the film containing e is exhibited.

[0042]

Next, the present invention will be further described with reference to examples. Using a galvanized steel sheet plated on a cold-rolled thin steel sheet by a conventional method, a predetermined zinc-based plating is performed by an example that is a method within the scope of the present invention and a comparative example that is a method outside the scope of the present invention. A steel sheet was prepared. The plating type of the galvanized steel sheet is one of the following symbols A, B, C, D, E, F and G.

A: 10 wt. % Fe and the balance of Zn are formed as galvannealed layers, and the adhesion amount is 6 on both sides.
0 g / m ² . B: A hot-dip galvanized layer was formed, and the adhesion amount was 90 g / m ² on both sides.

C: An electrogalvanized layer was formed, and the adhesion amount was 40 g / m ² on both sides. D: 15 wt. % Fe and the balance of Zn were formed on the electro-alloy plating layer, and the adhesion amount was 40 g / m ² on both sides.

E: 12 wt. % Ni and the balance of Zn are formed on the electro-alloy plating layer.
a / m ^2. F: 4 wt. % Cr and the balance of Zn were formed on the electro-alloy plating layer, and the adhesion amount was 20 g / m ² on both sides.

G: 5 wt. % Al and the balance of Zn are formed as a hot-dip alloy plating layer.
²

With respect to the galvanized steel sheets prepared by the methods of Examples and Comparative Examples in Tests 1 and 2 below, press formability, spot weldability, adhesiveness and chemical conversion treatment, and mechanical properties were evaluated. Was. The test method is as follows.

[Measurement of Coefficient of Friction] The measurement of the coefficient of friction is to measure the coefficient of friction between the specimen and the bead by the following method.

FIG. 4 is a schematic front view showing a friction coefficient measuring device. As shown in the figure, a sample 1 for measuring a coefficient of friction collected from a specimen is fixed to a sample table 2, and the sample table 2 is
It is fixed to the upper surface of a horizontally movable slide table 3. On the lower surface of the slide table 3, a vertically movable slide table support 5 having a roller 4 in contact therewith is provided.
The first load cell 7 for measuring the pressing load N on the friction coefficient measuring sample 1 by the beads 6 is attached to the slide table support 5 by pushing it up. I have. With the pressing force applied, a second end for measuring the sliding resistance F for moving the slide table 3 in the horizontal direction is provided at one end of the slide table 3 in the horizontal movement direction. A load cell 8 is attached to one end of the slide table 3. In addition, a press cleaning oil Preton R352L manufactured by Sugimura Chemical Co., Ltd. was used as a lubricating oil, and was applied to the surface of the sample 1 for friction coefficient measurement and tested.

The coefficient of friction μ between the specimen and the bead is
Formula: Calculated by μ = F / N. However, pressing load N: 400
kgf, sample withdrawal speed (horizontal movement speed of slide table 3): 100 cm / min.

FIG. 5 is a schematic perspective view showing the shapes and dimensions of the beads used. The lower surface of the bead 6 slides while being pressed against the surface of the sample 1. The underside shape is width 1
0 mm, a flat surface having a length of 3 mm in the sliding direction, and each of the front and rear surfaces having a width of 10 mm having a diameter of 4.5 mmR.
The / 4 cylindrical surface is in contact as shown in FIG.

[Continuous Dotting Test] Two specimens were piled up.
Resistance welding (spot welding) was carried out under the following welding conditions by sandwiching it with a pair of electrode tips of a spot welding machine from both sides and energizing under pressure to concentrate current.・ Electrode tip: dome type with tip diameter of 6 mm ・ Pressure: 250 kgf ・ Welding time: 12 cycles ・ Welding current: 11.0 KA ・ Welding speed: 1 point / sec.

As the evaluation of the continuous hitting property, the diameter of the molten and solidified metal part (shape: goishi shape, hereinafter referred to as nugget) generated at the joint of two welded base materials (specimens) during spot welding was evaluated. However, the number of spots obtained by continuous spot welding until the value became less than 4 × t ^1/2 (t: sheet thickness of one sheet) was used. The number of hit points is hereinafter referred to as an electrode life.

[Adhesion Test] The following test specimens for adhesion test were prepared from each specimen. FIG. 6 is a schematic perspective view illustrating the assembling process. As shown in FIG.
A test specimen 13 in which two test specimens 10 having a length of 200 mm and a length of 200 mm were overlapped and bonded via a spacer 11 having a diameter of 0.15 mm so that the thickness of the adhesive 12 became 0.15 mm.
And baking at 150 ° C. × 10 min.

The test specimen thus prepared was
As shown in FIG. 7, the sample was bent into a T-shape, and a tensile test was performed at a speed of 200 mm / min using a tensile tester, and the average peel strength (n = 3 times) when the test piece was peeled was measured. The peel strength was determined by calculating the average load from the load chart of the tensile load curve at the time of peeling, and expressed in units of kgf / 25 mm. In FIG. 7, P indicates a tensile load.

The adhesive used was a PVC-based hemming adhesive.

[Chemical conversion treatment test] Each specimen was treated with an immersion type zinc phosphate treating agent for an automotive coating base, and a zinc phosphate film was formed on the surface thereof. Then, the crystalline state of this film was observed with a scanning electron microscope (SEM). As a result, those with a normal zinc phosphate coating were evaluated as ○.
The mark, X, in which the zinc phosphate film was not formed or in which crystals were invisibly, was indicated by x.

[Material Test] The specimen was subjected to a tensile test to determine its yield point, tensile strength, elongation and drawing, and to evaluate its mechanical properties.

Hereinafter, Tests 1 to 3 will be described with reference to Examples and Comparative Examples. Table 1 summarizes the contents of each test. Tests 1 (test 1, 1, 1 and 1 of 3) and 2 mainly include the invention described in claims 1 and 2, and
Test 3 mainly describes the invention described in claims 3 and 4.

[0060]

[Table 1]

(Test 1) (Test 1-1) As shown in Table 2, the test conditions were as follows: a galvanized steel sheet having a plating type A (alloyed hot-dip galvanized) with a constant elongation of 0.7%. Tempering rolling before or after the alkali treatment, the alkali treatment having a pH of 9.5 to 1
Pre-treatment was performed by immersing in a 50 ° C. aqueous NaOH solution changed within the range of 4.0 for 5 seconds, and then the zinc-plated steel sheet after the pre-treatment was immersed in an aqueous solution containing FeCl ₂ and NiCl _2. Thus, an Fe—Ni—O-based film was formed on the surface. As a comparative example, alkali treatment was also performed using Fe
In the case where the -O-based film was not formed, the pre-treatment was performed but the Fe-Ni-O-based film was not formed, and the Fe-Ni-O-based film was formed without performing the alkali treatment. Was done.

[0062]

[Table 2]

Table 3 shows the test results. The table shows the following. Those with no Fe-Ni-O-based film formed on the surface are inferior in press formability, spot weldability, adhesion and chemical conversion treatment (Nos. 1 and 2). Even if an Fe—Ni—O-based film is formed, the alkali treatment at a pH of less than 10 is slightly inferior in press formability (Nos. 3 and 4).

On the other hand, in the examples, press formability, spot weldability, adhesiveness and chemical conversion treatment are improved (Nos. 5 to 14). Also, the pH of the alkali treatment solution
The larger the value, the greater the effect of improving press formability. These effects are the same regardless of whether temper rolling or alkali treatment is performed first in the pretreatment of the steel sheet.

[0065]

[Table 3]

(Test 1-2) As shown in Table 4, the test conditions were as follows: from a zinc-plated steel sheet having a plating type of A (alloyed hot-dip galvanized) to an elongation of 5. The temper rolling with the temperature changed to 5 is performed before or after the alkali treatment. The alkali treatment is performed by immersing in a NaOH aqueous solution at a constant value of pH 12.0 and a temperature of 50 ° C. for 5 seconds, and then the pretreatment is completed. Zinc-plated steel sheet
Immersion in an aqueous solution containing eCl ₂ and NiCl ₂
-A Ni-O based film was formed on the surface.

[0067]

[Table 4]

Table 5 shows the test results. The table shows the following. If the elongation ratio is less than 0.3% in the temper rolling in the pretreatment, the effect of improving the press formability is insufficient even if an Fe-Ni-O-based film is formed on the surface (No. 15 to 18). ). If the elongation exceeds 5.0%, the press formability, spot weldability, adhesiveness and chemical conversion properties are excellent, but the mechanical properties deteriorate (Nos. 29 and 30).

On the other hand, in Examples, press formability, spot weldability, adhesiveness and chemical conversion treatment are improved (Nos. 19 to 28). The effect of improving the press formability is greater when the elongation is increased by temper rolling. These effects are the same regardless of whether temper rolling or alkali treatment is performed first in the pretreatment of the steel sheet.

[0070]

[Table 5]

(Test 1-3) As shown in Table 6, the test conditions were as follows: a zinc-plated steel sheet having a plating type of A (alloyed hot-dip galvanized) was tempered at an elongation of 0.7% and a constant value. Rolling is performed, and the alkali treatment is performed by immersing in a 50 ° C. aqueous solution for 5 seconds while changing the type of the alkali component (however, some of the components are pH 2.0 and an acid component) at a fixed value of pH 12.0 ( However, some of them are pretreated by spraying the above aqueous solution, and then the zinc-plated steel sheet after the pretreatment is immersed in an aqueous solution containing FeCl ₂ and NiCl ₂ (however, some Was sprayed, electrolyzed or vapor-deposited on the aqueous solution to form a Fe—Ni—O-based film on the surface.

[0072]

[Table 6]

Table 7 shows the test results. The table shows the following. When the pretreatment is performed with an acidic aqueous solution containing an acid component, the effect of improving press formability is insufficient (Nos. 31 and 3).
2).

On the other hand, in Examples, press formability, spot weldability and adhesiveness were improved (No. 3).
3-41).

[0075]

[Table 7]

(Test 2) The test conditions are as shown in Table 8.
The plating type is changed to symbols B, C, D, E, F and G
The test was performed using a lead-based plated steel sheet. As an example,
Temper rolling at a constant value with an elongation of 0.7% on each steel sheet
It is applied before the alkali treatment, and the alkali treatment is pH 12.0
At a constant value of 50 ° C for 5 seconds
Pre-treated, then pre-treated zinc-based plated steel
The plate is made of FeCl_TwoAnd NiCl _TwoImmersion in an aqueous solution containing
As a result, an Fe—Ni—O-based film was formed on the surface. In addition,
As comparative examples, temper rolling and alkali treatment,
Not perform all of the formation of the Fe—Ni—O-based coating
And alkali treatment was performed, but temper rolling was performed.
We just tested the case where Fe-Ni-O-based film was formed
did.

[0077]

[Table 8]

Table 9 shows the test results. The table shows the following. Regardless of the type of plating, if all of the temper rolling and alkali treatment and the formation of the Fe—Ni—O-based film were not performed, the press formability, spot weldability, and adhesion were poor (No) .42, 45, 48, 51,
54 and 57). Further, in the conditions of the present invention, when only temper rolling is not performed, only the press formability is improved to some extent because the Fe-Ni-O-based film is formed on the surface, but it is not sufficient. No (No. 43, 46, 4
9, 52, 55 and 58).

On the other hand, in Examples, press formability, spot weldability and adhesiveness were improved (No. 4).
4, 47, 50, 53, 56 and 59).

[0080]

[Table 9]

(Test 3) As shown in Tables 10 and 11, the test conditions were as follows: A zinc-plated steel sheet having a plating type of A (alloyed hot-dip galvanized) was treated with a constant temper at an elongation of 0.7%. Rolling is performed before or after the alkali treatment, and the alkali treatment is performed by immersing in a NaOH aqueous solution at a constant value of pH 12.0 and a temperature of 50 ° C. for 5 seconds, and then the galvanized steel sheet having been subjected to the pretreatment is FeCl ₂ and NiCl
_It was immersed in an aqueous solution containing ₂ to form an Fe-Ni-O-based film on the surface. Here, FeCl ₂ and NiC in the aqueous solution
l ₂ as a constant value of 200 g / l, and Fe with respect to the sum of the Fe content (wt.%) and the Ni content (wt.%).
The ratio of the content (wt.%) Was variously changed within the range of 0 to 1. The pH of this aqueous solution was 2.5 and the temperature was 50 ° C.

[0082]

[Table 10]

[0083]

[Table 11]

The test results are shown in Tables 12 and 13.
The table shows the following. In the comparative example, Fe / (Fe + Ni) in the aqueous solution for forming a Fe—Ni—O-based film was 0. Therefore, when a Ni—O-based film was formed, the press formability and the adhesiveness were poor (No. 60 and 79). On the other hand, Fe / (Fe + N
When i) is 1, therefore, when the Fe—O-based film is formed, the press formability and the spot weldability are poor (No. 7).
8 and 97).

On the other hand, in the examples, press formability, spot weldability, adhesiveness and chemical conversion property are improved (Nos. 61 to 77 and 80 to 96). In particular,
When Fe / (Fe + Ni) is in the range of 0.004 to 0.9, the improvement is further improved. These effects are the same regardless of whether temper rolling or alkali treatment is performed first in the pretreatment of the steel sheet.

[0086]

[Table 12]

[0087]

[Table 13]

[0088]

The present invention is configured as described above.
Fe- formed on the surface of the plating layer of zinc-based plated steel sheet
Since the performance of the Ni-O-based coating is improved, and it is harder than the zinc or zinc alloy plating layer and has a high melting point, the sliding resistance between the plating layer surface and the press die during press molding is reduced. As a result, the zinc-plated steel sheet easily slides into the press die, and the press formability is improved. In addition, Fe-
The presence of the Ni-O-based high-melting film improves the continuous spotting property in spot welding. Furthermore, the adhesiveness is improved by the presence of the Fe—Ni—O-based coating. As described above, the present invention can provide a method for producing a galvanized steel sheet having excellent press formability, spot weldability, and adhesiveness, and has an industrially useful effect.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of a relationship between a Ni adhesion amount to a zinc-based plated steel sheet and a friction coefficient when an alkali solution treatment and a temper rolling are performed and not performed.

FIG. 2 is a graph showing the difference in the amount of Ni deposited on a zinc-based plated steel sheet when immersed in a chloride bath, a sulfuric acid bath, and a nitric acid bath as a treatment liquid for forming an Fe—Ni—O-based film.

FIG. 3 is a graph showing an example of the amount of Ni adhering to a galvanized steel sheet with respect to the immersion time when the pH is changed.

FIG. 4 is a schematic front view showing a friction coefficient measuring device.

FIG. 5 is a schematic perspective view showing the shape and dimensions of a bead in FIG.

FIG. 6 is a schematic perspective view illustrating a process of assembling a test specimen for an adhesion test.

FIG. 7 is a schematic perspective view illustrating a load of a tensile load when a peel strength is measured in an adhesion test.

[Explanation of symbols]

 1 Sample for friction coefficient measurement, 2 Sample table, 3 Slide table, 4 Roller, 5 Slide table support, 6 Bead, 7 First load cell, 8 Second load cell, 9 Ray 10 specimens, 11 spacers, 12 adhesives, 13 specimens for adhesion test, P tensile load, F sliding resistance, N pressing load.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Junichi Inagaki 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Masaaki Yamashita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Ryuji Nagayama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-9-209160 (JP, A) JP-A-9-263923 (JP) , A) JP-A-9-263965 (JP, A) WO 96/10103 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 2/00-2/40 C23C 22 / 00-22/86 C23C 28/00-30/00 C25D 3/00-7/12

Claims (4)

(57) [Claims] 1. A temper rolling is performed on a galvanized steel sheet with an elongation percentage in the range of 0.3 to 5.0%, and a pH of 10 or more is applied to the temper-rolled galvanized steel sheet. Alkali treatment with an alkali solution for 2 to 30 seconds, and then forming a Fe-Ni-O-based coating on the surface of the plating layer of the zinc-coated steel sheet that has been subjected to the alkali treatment. Production method. 2. A galvanized steel sheet is subjected to alkaline treatment with an alkaline solution having a pH of 10 or more for 2 to 30 seconds.
The temper rolling is performed on the zinc-plated steel sheet subjected to the alkali treatment so that the elongation percentage is in a range of 0.3 to 5.0%. A method for producing a zinc-based plated steel sheet, comprising forming an Fe-Ni-O-based coating on a surface of a plating layer. 3. The method of forming an Fe—Ni—O-based film according to claim 1, wherein the method includes FeCl ₂ and NiCl ₂ and has a pH of 2.
The method for producing a galvanized steel sheet according to claim 1, wherein the galvanized steel sheet is treated with an aqueous solution having a temperature within a range of 0 to 3.5 and a temperature within a range of 20 to 70 ° C. 4. . 4. The formation of the Fe—Ni—O-based coating is performed by F
eCl ₂ and NiCl ₂ , Fe content (wt.
%) And the Ni content (wt.%), The ratio of the Fe content (wt.%) Is in the range of 0.004 to 0.9, and the pH is 2.0 to 3.5. Within the range and at a temperature of 20
The method for producing a galvanized steel sheet according to claim 1 or 2, wherein the galvanized steel sheet is treated with an aqueous solution having a temperature within a range of -70 ° C.