JPH09263966A - Production of galvanized steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a film having hardness and the m.p. higher than those of a galvanizing layer in a galvanized steel sheet and by which the peeling strength of the adhesion sheet is made good on the surface of the surface of the galvanized steel sheet. SOLUTION: A galvanized steel sheet is subjected to skinpass rolling at 0.3 to 5.0% elongation percentage. After or before that, treatment is executed for 2 to 30sec by an alkali soln. of >=pH10, and next, an Fe-Ni-O film is formed on the surface of the plating layer. As for the formation of the Fe-Ni-O film. treatment is executed by an aq. slon. of pH2.0 to 3.5 contg. Fe-Cl2 and heated at 20 to 70 deg.C. Furthermore, the condition in which the ratio of the Fe content (wt.%) to the total of the Fe content (wt.%) and Ni content (wt.%) is regulated to 0.004 to 0.9 is added. In this way, the method for producing the galvanized steel sheet excellent in press formability, spot weldability and adhesive properties can be provided.

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

However, zinc-based plated steel sheets generally have a drawback that they are inferior in press formability to cold-rolled steel sheets. This is because the sliding resistance between the zinc-based plated steel sheet and the press die is higher than that in the case of cold-rolled steel sheet.If this sliding resistance is high, near the bead part of the die during pressing. It becomes difficult for the galvanized steel sheet to flow into the press die, and the steel sheet easily breaks.

As a method of 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 are problems such as a coating defect due to poor degreasing in the next coating step, and oil depletion, which causes unstable press performance. There is a high demand for improvement in press formability of galvanized steel sheets.

On the other hand, in a zinc-based plated steel sheet, copper, which is an electrode, reacts with molten zinc during spot welding to easily form a brittle alloy layer, so that the copper electrode is greatly worn and its life is short. There is a problem that it is inferior in continuous spotting property to cold-rolled steel sheets.

Further, in the manufacturing process of an automobile body,
Although various adhesives are used for the purpose of rust prevention and vibration control, it has recently become clear that zinc-based plated steel sheets are inferior in adhesiveness to cold-rolled steel sheets.

As a method for solving the above problem, Japanese Patent Laid-Open No.
JP-A-190483 discloses that an electrolytic film, a dipping process, a coating oxidation process, or a heating process is performed on the surface of a zinc-based plated steel sheet to generate an oxide film mainly composed of ZnO, thereby improving weldability or workability. The technology (hereinafter, referred to as "prior art 1") is disclosed.

[0008] JP-A-3-17282 discloses that Fe, N
A method of substituting one or more selected from i and Co on the surface of a zinc-based plated steel sheet (hereinafter,
"Prior Art 2") is disclosed in Japanese Patent Laid-Open No. 3-1.
Japanese Patent Laid-Open No. 91093 discloses a technique (hereinafter, referred to as "Prior Art 3") for improving press moldability and chemical conversion treatability by generating Ni oxide.
Japanese Patent Laid-Open No. 94 discloses a method of applying an aqueous solution of an inert film component (hereinafter referred to as "prior art 4").

Further, JP-A-4-21751 discloses that a galvanized steel sheet containing Al in a plating layer contains an oxidizing agent having an oxidizing power to Zn metal and has a pH of 1 or less.
Disclosed is a method (hereinafter referred to as "Prior Art 5") of contacting an alkaline solution having a liquid temperature of 1 or more and a temperature of 40 ° C or more.

[0010]

The above-mentioned prior art 1 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 sliding resistance between the press die and the plated steel sheet is small, and the effect of improving press formability is small. Is small. Further, an oxide mainly composed of ZnO deteriorates the adhesiveness.

Prior art 2 has the following problems. Although a method of depositing a metal such as Ni and Fe improves corrosion resistance, sufficient adhesion cannot be obtained because the wettability of the metal to the adhesive is small. In addition, there is a problem that the effect of improving press formability and spot weldability is small because the coating has strong metallic properties. Furthermore, since the pH of the aqueous solution is low and the substitution precipitation efficiency is low, it is not possible to secure a sufficient amount of deposition, and it is necessary to raise the temperature of the aqueous solution to secure the amount of deposition. There is a problem in that the production cost rises because of the rise in temperature and the provision of heating equipment for the aqueous solution.

The spot weldability refers to the continuous spotting property in the spot welding of thin steel sheets, and the number of times the spot welding can be performed continuously without having to care for or replace the electrode tip of the welding. , Which is consistent with the life of the electrode that can be continuously used.

Since the prior art 3 is a Ni oxide single phase film, it has a problem that the press formability is improved but the adhesiveness is deteriorated. Since the prior art 4 is a method of forming an inactive film, it has a problem that chemical conversion processability and adhesiveness deteriorate.

Prior art 5 is a method of forming an oxide film mainly composed of Zn hydroxide and oxide containing no Al on a hot-dip galvanized steel sheet containing Al in the plating layer. Similar to the technique 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.

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

[0016]

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

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

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

The continuous spotting property in spot welding of a zinc-based plated steel sheet is inferior to that of a cold-rolled steel sheet because zinc melted during welding and copper of the electrode come into contact with each other to form a brittle alloy layer on the electrode surface. This is because the generation of the electrode causes severe deterioration of the electrode. As a method of improving the continuous spotting property of a zinc-based plated steel sheet, it is considered effective to form a high melting point film on the plated surface. The present inventors have studied various coatings in order to improve the spot weldability of zinc-based plated steel sheets, and have found that the 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 point Zn—Ni alloy, and the Ni oxide has a very high melting point.
Further, it is considered that the electrical conductivity is high due to the semiconductor property.

It was known that the adhesiveness of the zinc-based plated steel sheet was inferior to that of the cold-rolled steel sheet, but the cause was not clear. As a result of investigating this cause, the present inventors have found that the adhesiveness is controlled by the composition of the oxide film on the surface of the steel sheet. That is,
In the case of cold-rolled steel sheet, the oxide film on the steel sheet surface is mainly Fe oxide, whereas in the case of zinc-based plated steel sheet, Zn oxide is
Mainly oxides. 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 becomes possible to improve the adhesiveness by forming Fe oxide on the surface of the zinc-plated steel sheet as in the present invention.

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

According to a second aspect of the present invention, there is provided a method for manufacturing a zinc-based plated steel sheet, wherein the zinc-based plated steel sheet is subjected to alkali treatment with an alkaline solution having a pH of 10 or more for 2 to 30 seconds, and the zinc-plated steel sheet subjected to the alkali treatment is treated. And the extension rate is 0.3-
After the temper rolling within the range of 5.0%, Fe-Ni- is then applied to the surface of the plated layer of the temper-rolled zinc-based plated steel sheet.
It is characterized by forming an O-based film.

A method for producing a zinc-based plated steel sheet according to claim 3 is the method according to claim 1 or 2, wherein Fe-N is used.
As a method for forming the i-O-based film, FeCl ₂ and NiCl ₂ are contained, the pH is 2.0 to 3.5, and the temperature is 2
It is characterized by treating a zinc-based plated steel sheet with an aqueous solution of 0 to 70 ° C.

The method for producing a zinc-plated steel sheet according to claim 4 is the method according to claim 1 or 2, wherein Fe--N
As a method of the i-O-based film forming treatment, FeCl ₂ and NiCl ₂ are contained, and the Fe content (wt.%) with respect to the sum of the Fe content (wt.%) and the Ni content (wt.%) is The ratio is 0.004 to 0.9, the pH is 2.0 to 3.5, and the temperature is 2.
It is characterized by treating a zinc-based plated steel sheet with an aqueous solution of 0 to 70 ° C.

In this application, Fe as an upper layer formed on the surface of the plating layer of the zinc-based plated steel sheet.
When referring to a -Ni-O type film, it is called a "film", while
When referring to the zinc-based plating layer as the lower layer, it is called a "plating layer" and not a "coating".

[0027]

Next, the reason for limiting the manufacturing conditions of the present invention as described above will be described. In the present invention, the zinc-based plated steel sheet is treated with an alkaline solution having a pH of 10 or more for 2 to 30 seconds and then a Fe-Ni-O-based coating is formed on the surface of the zinc-based plated steel sheet. This is because the press moldability is remarkably excellent in the case of performing the alkali treatment as compared with the case of forming the Fe-Ni-O-based film without the treatment with the solution. Also, before or after treatment with an alkaline solution,
When the Fe-Ni-O-based film is formed after the temper rolling within the range of the elongation rate of 0.3% to 0.5%, the surface of the zinc-based plated steel sheet is smoothed by the temper rolling, and Fe
This is because the oxide film or the like that inhibits the adhesiveness of the —Ni—O-based coating is removed, so that the adhesiveness is improved and a zinc-based plated steel sheet exhibiting excellent press formability can be obtained.

FIG. 1 is a graph showing the relationship between the amount of Ni adhered to the surface of the plated layer and the friction coefficient of a zinc-based plated steel sheet, with and without alkali solution treatment and temper rolling. is there. From the figure, when the alkaline solution treatment and temper rolling are performed, the friction coefficient value becomes smaller for the same Ni deposition amount than in the case where the treatment is not performed, which is excellent in press formability. You can see that Here, the alkaline solution is NaOH, KOH,
Na ₂ SO ₄ , Na ₂ PO ₄ , LiOH and MgOH
It is possible to use one or more aqueous solutions of alkaline chemicals such as. Further, the alkaline concentration of the aqueous solution requires that the pH is 10 or more, but p
It is more desirable to adjust H to be 11 or more. In that case, the concentration is generally 5 to 50 g / l.

On the other hand, when the Fe-Ni-O-based coating is formed after treating the zinc-based plated steel sheet with the acidic solution, the press formability is slightly improved,
The press formability, spot weldability and adhesiveness are inferior to the case of treatment with an alkaline solution. This is because by treating the zinc-based plated steel sheet with an alkaline solution, the adhesiveness of the Fe-Ni-O-based coating formed thereafter is improved. With an acidic solution, the surface of the zinc-based plated steel sheet is unavoidable. It is considered that the above effect cannot be obtained because the amount of the oxide film generated in the above increases.

Here, the Fe-Ni-O-based coating is a mixture of Fe metal, Fe oxide, Ni metal and Ni oxide, and the method of forming this coating is not particularly limited, and iron is not used. 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 the aqueous solution, a spraying method and a coating method of the aqueous solution, an electroplating method, or the like. Further, a vapor phase plating method such as laser CVD, photo CVD, vacuum vapor deposition and sputter vapor deposition can be adopted.

In addition, Zn, Co, Mn, Mo, A contained in the plating layer of the zinc-based plated steel sheet used in the present invention is inevitably contained in the above-mentioned aqueous solution for film formation.
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 alkaline solution in order to enhance the alkali treatment of the zinc-based plated steel sheet. However, the addition of an oxidant or the like is not desirable because an oxide is formed on the surface of the zinc-plated steel sheet and the adhesion of the Fe-Ni-O-based coating deteriorates.

Next, regardless of the order of temper rolling and alkali treatment performed before the Fe-Ni-O-based coating forming treatment, there is a factor that inhibits the amount of Fe-Ni-O-based coating deposited. If removed, the same effect can be obtained. Therefore, the order effective for removing the inhibiting factors may be appropriately selected depending on the type of zinc-based plated steel sheet. Further, regarding the elongation ratio of temper rolling, it is sufficient to remove the factor that inhibits the adhesion of the Fe-Ni-O-based coating, and for that purpose, 0.3 to 5.0% is required.
However, if the elongation rate is the same, the greater the reduction load, the greater the effect. Extension rate is 0.3
If it is less than%, the smoothing effect is small and satisfactory press formability cannot be obtained. On the other hand, if the extension rate exceeds 5.0%,
This is not desirable because the material deteriorates.

In claims 3 and 4, 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 the use of a metal salt of chloride for supplying ferric ions and nickel ions leads to high precipitation efficiency, and therefore productivity can be improved. . When the salt concentration and treatment time are the same, Ni and Fe are more
The adhered amount of is increased.

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

The pH of the aqueous solution for film formation is 2.0 to
It is desirable to set it 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 will be extremely large, the deposition efficiency will be low, and the amount of Ni and Fe deposited will be small at the same salt concentration and treatment time, resulting in reduced productivity. is there. Further, the film is mainly composed of Ni and Fe metal, and the effect of improving press formability, spot weldability and adhesiveness cannot be obtained. On the other hand, pH
When the value exceeds 3.5, Fe in the aqueous solution is heavily oxidized, and sludge causes defects on the surface of the steel sheet.

FIG. 3 is a graph showing an example of the Ni adhesion amount with respect to the immersion time when the pH is changed from 2.0 to 3.5. The treatment bath temperature was 50 ° C., the concentration ratio of Ni and Fe in the treatment bath was 20:80, and the total concentration was 100.
It is the case of g / l, and it is understood that the precipitation efficiency is better when the pH is higher.

The temperature of the aqueous solution for film formation is 20 to 70 ° C.
Is desirably within the range. The reason is as follows. When the temperature of the aqueous solution is lower than 20 ° C., the reaction rate is slow, and it takes a lot of time to secure the amount of Ni and Fe adhered necessary for improving the characteristics of the film, resulting in a decrease in productivity. On the other hand, when the temperature of the aqueous solution exceeds 70 ° C., the performance deterioration of the aqueous solution progresses rapidly, and equipment and heat energy for keeping the temperature at high temperature are required, which causes an increase in manufacturing cost.

In claims 3 and 4, Fe-Ni-
Fe content (w
t. %) And the Ni content (wt.%) Plus Fe
Ratio of content (wt.%) (Hereinafter, Fe ratio: Fe /
(Fe + Ni) is limited to within the range of 0.004 to 0.9 when less than 0.004, there is no effect of improving the adhesiveness, while when it exceeds 0.9, the spot weldability of This is because the improvement effect is small.

The zinc-based 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 dipping method, an electroplating method, a vapor phase plating method or the like. The composition of the plating layer on the surface of this zinc-based plated steel sheet is not only pure zinc but also Fe, Ni, Co,
Mn, Cr, Al, Mo, Ti, Si, W, Sn, P
Metals such as b, Nb, and Ta (however, Si is also treated as a metal) or oxides, or one or two of organic substances.
It may consist of a single-layer or multi-layer plating layer containing one or more species. In addition, SiO ₂ and Al ₂ O are added to the plated layer.
_It may contain fine particles such as ₃ . 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-based film formed on the surface of the plating layer of the zinc-based plated steel sheet under the above-mentioned limiting conditions eliminates the phenomenon of adhesion between the steel sheet and the mold during press forming, resulting in a sliding resistance. It becomes smaller, slips better into the mold, suppresses the formation of a brittle alloy layer with the electrode copper during spot welding, and improves continuous spotting properties.
The effect of the adhesiveness is improved by the effect of the film containing e.

[0042]

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

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

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

E: 12 wt. % Ni, the balance Zn is an electro-alloy plating layer is formed, and the adhesion amount is 30 g on both sides.
a / m ^2. F: 4 wt. An electric alloy plating layer containing% Cr and the balance Zn is formed, and the amount of the adhesion is 20 g / m ² on both surfaces.

G: 5 wt. % Al and the balance Zn, a molten alloy plating layer is formed, and the adhesion amount is 60 g / m on both sides.
²

With respect to the zinc-plated steel sheets prepared by the methods of Examples and Comparative Examples in the following Tests 1 and 2, the press formability, spot weldability, adhesiveness and chemical conversion treatability, and mechanical properties were evaluated. It was The test method is as follows.

[Measurement of Friction Coefficient] In the friction coefficient measurement, the friction coefficient between the sample and the bead is measured by the following method.

FIG. 4 is a schematic front view showing the 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.
Is provided, and a first load cell 7 for measuring the pressing load N on the friction coefficient measuring sample 1 by the bead 6 is attached to the slide table support 5 by pushing it up. There is. A second portion for measuring a sliding resistance force F for horizontally moving the slide table 3 is provided at one end portion of the slide table 3 in the horizontal movement direction while the pressing force is applied. A load cell 8 is attached to one end of the slide table 3. As the lubricating oil, press cleaning oil Preton R352L manufactured by Sugimura Chemical Co., Ltd. was used and applied to the surface of the friction coefficient measurement sample 1 for testing.

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 withdrawing speed (horizontal moving speed of slide table 3): 100 cm / min.

FIG. 5 is a schematic perspective view showing the shape 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 RBI Test] Two test specimens are stacked,
Resistance welding (spot welding) in which it was sandwiched by a pair of electrode tips of a spot welding machine from both sides and current was concentrated by applying pressure was continuously carried out under the following welding conditions.・ Electrode tip: dome type with a tip diameter of 6 mm ・ Pressure force: 250 kgf ・ Welding time: 12 cycles ・ Welding current: 11.0 KA ・ Welding speed: 1 point / sec.

The diameter of the melted and solidified metal portion (shape: go-stone shape, hereinafter referred to as a nugget) formed at the joint between two welded base materials (specimen) during spot welding was evaluated as continuous spotting property. Was 4 × t ^1/2 (t: plate thickness of one sheet), and the number of consecutively welded spots was used. In addition, the above-mentioned number of dots was set as the electrode life.

[Adhesiveness Test] The following adhesiveness test specimens were prepared from each specimen. FIG. 6 is a schematic perspective view illustrating the assembly process. As shown in FIG.
Specimen 13 in which two test pieces 10 having a length of m and a length of 200 mm are stacked and adhered so that the thickness of the adhesive 12 is 0.15 mm with a spacer 11 having a diameter of 0.15 mm therebetween.
And baking at 150 ° C. × 10 min.

The test body thus prepared was
As shown in FIG. 7, the sample was bent into a T-shape, and a tensile tester was used to perform a tensile test at a speed of 200 mm / min to measure the average peel strength (n = 3 times) when the test body peeled. 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.

As the adhesive, a vinyl chloride-based hemming adhesive was used.

[Chemical Conversion Treatability Test] Each sample was treated with an immersion type zinc phosphate treating agent for automobile coating bases to form a zinc phosphate film on its surface. Then, the crystalline state of this film was observed with a scanning electron microscope (SEM). As a result, if the zinc phosphate film is normally formed,
Marks, those in which the zinc phosphate film was not formed or in which crystals were not visible were indicated by x marks.

[Material Test] A tensile test was performed on the test piece to determine the yield point, tensile strength, elongation and reduction, and the mechanical properties were evaluated.

Tests 1 to 3 will be described below with respect to Examples and Comparative Examples. Table 1 shows an outline of each test content. Tests 1 (test 1, 1, 1 and 2 and 1 of 3) and 2 mainly comprise the invention described in claims 1 and 2, and
Test 3 mainly explains the invention described in claims 3 and 4.

[0060]

[Table 1]

(Test 1) (1 of Test 1) As shown in Table 2, the test conditions are constant at an elongation rate of 0.7% on a zinc-based plated steel sheet whose plating type is the symbol A (hot dip galvannealing). Value temper rolling is performed before or after the alkali treatment, and the alkali treatment has a pH of 9.5 to 1
Pretreatment is performed by immersing in a 50 ° C. NaOH aqueous solution changed within the range of 4.0 for 5 seconds, and then the pretreated zinc-based plated steel sheet is immersed in an aqueous solution containing FeCl ₂ and NiCl _2. To form a Fe-Ni-O-based coating on the surface. In addition, as a comparative example, the alkali treatment is also performed with Fe-Ni
In the case where the -O-based film was not formed, the pretreatment was performed but the Fe-Ni-O-based film was not formed, and the Fe-Ni-O-based film was formed without the alkali treatment. If you did.

[0062]

[Table 2]

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

On the other hand, in the examples, the press formability, spot weldability, adhesiveness and chemical conversion treatability are improved (No. 5-14). Also, the pH of the alkaline treatment solution
The larger the value, the greater the effect of improving press formability. These effects do not change whether the temper rolling or the alkali treatment is performed first in the pretreatment of the steel sheet.

[0065]

[Table 3]

(Test 1-2) As shown in Table 4, a zinc-based plated steel sheet having a plating type of symbol A (hot-dip galvannealed) was subjected to temper rolling at a stretch ratio of 5. The temper rolling that has been changed to 5 is performed before or after the alkali treatment, and the alkali treatment is performed by immersing the solution in a NaOH aqueous solution at a temperature of 50 ° C for 5 seconds at a constant value of pH 12.0 to finish the pretreatment. The zinc-plated steel sheet
Fe immersed in an aqueous solution containing eCl ₂ and NiCl ₂
-Ni-O based film was formed on the surface.

[0067]

[Table 4]

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

On the other hand, in Examples, the press formability, spot weldability, adhesiveness and chemical conversion treatability are improved (No. 19 to 28). Moreover, the effect of improving press formability is greater when the elongation is increased by temper rolling. These effects do not change whether the temper rolling or the 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 are as follows: a zinc-plated steel sheet having a plating type of symbol A (hot dip galvanizing) is a tempered material with an elongation of 0.7% and a constant value. Rolling is carried out, and alkali treatment is carried out by changing the kind of alkali component (however, some components are acid components at pH 2.0) at a constant value of pH 12.0, and immersing in an aqueous solution at 50 ° C for 5 seconds ( However, some of them are pre-treated by spraying the above aqueous solution, and then the pretreated zinc-based plated steel sheet is immersed in an aqueous solution containing FeCl ₂ and NiCl ₂ (however, some are Was sprayed, electrolyzed, or vapor-deposited with the above aqueous solution to form a Fe-Ni-O-based coating on the surface.

[0072]

[Table 6]

Table 7 shows the test results. The table shows the following. If the pretreatment is performed with an acidic aqueous solution containing an acid component, the effect of improving press moldability is insufficient (No. 31 and 3).
2).

On the other hand, in the examples, the press formability, spot weldability and adhesiveness are 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 the symbols B, C, D, E, F and G
The test was performed using a lead-based plated steel sheet. As an example,
Each steel sheet is temper-rolled at a constant value with an elongation of 0.7%.
It is given before the alkali treatment, and the pH of the alkali treatment is 12.0.
At a constant value of 50 ° C for 5 seconds
Pre-treated, then pre-treated zinc-plated steel
Plate, FeCl_TwoAnd NiCl _TwoImmersion in an aqueous solution containing
Then, an Fe-Ni-O-based film was formed on the surface. In addition,
As a comparative example, temper rolling and alkali treatment,
In addition, the formation of the Fe-Ni-O-based coating was not performed at all.
However, temper rolling was performed.
First, test with the case of forming Fe-Ni-O based film
did.

[0077]

[Table 8]

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

On the other hand, in the examples, the press formability, spot weldability and adhesiveness are 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-based plated steel sheet with a plating type of A (hot dip galvannealing) was used for tempering at a constant value with an elongation of 0.7%. Rolling is performed before or after the alkali treatment, and the alkali treatment is performed by dipping in a NaOH aqueous solution at a temperature of 50 ° C. at a constant value of pH 12.0 for 5 seconds to perform pretreatment, and then the zinc-based plated steel sheet on which the pretreatment is finished, FeCl ₂ and NiCl
_It was dipped in an aqueous solution containing ₂ to form a Fe-Ni-O-based film on the surface. Here, FeCl ₂ and NiC in the aqueous solution
Fe with respect to the sum of the Fe content (wt.%) and the Ni content (wt.%), with the total concentration with l _{2 being} a constant value of 200 g / l.
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 Fe-Ni-O-based film forming aqueous solution was 0. Therefore, when the 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, and therefore a Fe-O based film is formed, the press formability and spot weldability are poor (No. 7).
8 and 97).

On the other hand, in the examples, the press formability, spot weldability, adhesiveness and chemical conversion treatability are improved (Nos. 61 to 77 and 80 to 96). Especially,
When Fe / (Fe + Ni) is in the range of 0.004 to 0.9, it is further improved. These effects do not change whether the temper rolling or the 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 Ni-O-based coating has improved performance, 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 high. As a result, the zinc-based plated steel sheet easily slips into the press die, and press formability is improved. In addition, Fe-
The presence of the Ni—O-based high melting point film improves the continuous spotting property in spot welding. Furthermore, the presence of the Fe-Ni-O-based coating improves the adhesiveness. As described above, the present invention can provide a method for producing a zinc-based plated steel sheet excellent in press formability, spot weldability, and adhesiveness, and brings an extremely useful effect industrially.

[Brief description of drawings]

FIG. 1 is a graph showing an example of the relationship between the amount of Ni adhered to a zinc-based plated steel sheet and the friction coefficient with and without alkali solution treatment and temper rolling.

FIG. 2 is a graph showing the difference in the amount of Ni deposited on a zinc-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 coating.

FIG. 3 is a graph showing an example of the amount of Ni adhered to the zinc-based plated 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.

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

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

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

[Explanation of symbols]

 1 sample for friction coefficient measurement, 2 sample stage, 3 slide table, 4 roller, 5 slide table support, 6 beads, 7 first load cell, 8 second load cell, 9 rail 10 specimens, 11 spacers, 12 adhesives, 13 adhesion test specimens, P tensile load, F sliding resistance, N pressing load.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location C25D 5/48 C25D 5/48 (72) Inventor Junichi Inagaki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo No. Japan Steel Pipe Co., Ltd. (72) Inventor Masaaki Yamashita 1-2, Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Ryuji Nagayama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Main Steel Pipe Co., Ltd.

Claims (4)

[Claims] 1. A zinc-based plated steel sheet is temper-rolled with an elongation in the range of 0.3 to 5.0%, and the temper-rolled zinc-based plated steel sheet has a pH of 10 or more. An alkaline solution is applied for 2 to 30 seconds, and then an Fe-Ni-O-based coating is formed on the surface of the plated layer of the zinc-based plated steel sheet that has been subjected to the alkaline treatment. Production method. 2. A zinc-based plated steel sheet is alkali-treated for 2 to 30 seconds with an alkaline solution having a pH of 10 or more,
The alkali-treated zinc-plated steel sheet is subjected to temper rolling with an elongation within the range of 0.3 to 5.0%, and then the temper-rolled zinc-based plated steel sheet A method for producing a zinc-based plated steel sheet, which comprises forming an Fe-Ni-O-based film on the surface of the plated layer. 3. The method of forming the Fe—Ni—O-based film contains FeCl ₂ and NiCl ₂ and has a pH of 2.
The method for producing a zinc-based plated steel sheet according to claim 1 or 2, wherein the zinc-based plated steel sheet is treated with an aqueous solution within a range of 0 to 3.5 and a temperature within a range of 20 to 70 ° C. . 4. The formation of the Fe—Ni—O based film is performed by F
It contains eCl ₂ and NiCl _{2 and} has a 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 temperature is 20
The method for producing a zinc-based plated steel sheet according to claim 1 or 2, wherein the zinc-based plated steel sheet is treated with an aqueous solution in the range of ~ 70 ° C.