JP3111886B2 - Manufacturing method of high lubrication alloyed hot-dip galvanized steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a highly lubricated galvanized steel sheet, and more particularly to a method for producing a highly lubricated galvanized steel sheet having excellent surface appearance and easy defect detection.

[0002]

2. Description of the Related Art Alloyed hot-dip galvanized steel sheets are widely used as various rust-preventive steel sheets because of their various excellent features.

In order to use this alloyed hot-dip galvanized steel sheet as a rust-preventive steel sheet for automobiles, in addition to corrosion resistance and coating compatibility, in addition to the performance required in the vehicle body manufacturing process,
It is important that they have excellent press formability, spot weldability, adhesiveness, and chemical conversion treatment properties, and that they can be supplied to consumers at low cost, that is, the production cost is low.

[0004] However, alloyed hot-dip 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 galvannealed steel sheet and the press die is higher than that of the cold-rolled steel sheet. The alloyed hot-dip galvanized steel sheet in the vicinity of the portion becomes difficult to flow into the press die, and the steel sheet is easily broken.

As a method for improving the press formability of an alloyed hot-dip galvanized steel sheet, generally, a method of applying a high-viscosity lubricating oil is widely used.
Due to the high viscosity of the lubricating oil, there are problems such as coating defects due to poor degreasing in the next coating step, press molding instability due to lack of lubricating oil, and instability in press performance.

[0006] In recent years, therefore, a two-layer plated steel sheet in which an iron-based plating film is formed by electroplating on the surface of a plated layer of an alloyed hot-dip galvanized steel sheet has been used.

[0007] The iron-based plating film has the effect of reducing the sliding resistance during press molding and improving the coating compatibility.

However, in order to manufacture this double-layered steel sheet with hot-dip galvanizing equipment (CGL), it is necessary to add an electro-galvanizing equipment. That is, there is a problem that the manufacturing cost is increased.

As a method for solving the above problem, Japanese Patent Laid-Open No.
JP-A-190483 discloses that 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 to improve weldability or workability. Japanese Patent Application Laid-Open No. Hei 3-17282 discloses a technique for causing
Japanese Patent Application Laid-Open No. 3-191 discloses a method in which one or two or more metals selected from Fe, Ni and Co are substituted and precipitated on the surface of a zinc-based plated steel sheet.
Japanese Patent Application Publication No. 093 discloses a technique for producing a Ni oxide to improve press formability and chemical conversion treatment (hereinafter, Prior Art 3).
And JP-A-60-63394 discloses a method for applying an aqueous solution of an inert coating component (hereinafter referred to as prior art 4).

[0010]

The prior art 1 described above has the following problems. In Prior Art 1,
Since various processes are used to generate oxides mainly composed of ZnO on the plating surface, 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. Further, an oxide mainly composed of ZnO deteriorates adhesiveness.

The prior art 2 has the following problems. In the prior art 1, since a metal such as Ni or Fe is deposited, sufficient adhesion cannot be obtained because the wettability with respect to the adhesion of the metal is small. In addition, there is a problem that the effect of improving press formability and spot weldability is small due to the strong metallic properties of the coating.

In addition, 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 adhesion, and it is necessary to raise the temperature of the aqueous solution in order to secure the amount of adhesion. However, there is a problem that the equipment cost is increased, for example, by causing an increase in the temperature and providing a heating equipment for the aqueous solution.

In Prior Art 3, since it is a single-phase oxide film of Ni oxide, press formability is improved, but there is a problem that adhesion is deteriorated.

In prior art 4, since it is a method of forming an inert film, there is a problem that the chemical conversion property and the adhesion are deteriorated.

The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and have filed Japanese Patent Application No. 7-216589 by the same applicant as FeCl ₂ and NiCl _2.
And the Fe content (g / l) and the Ni content (g /
l) and the ratio of the Fe content (g / l) to the sum of
An aqueous solution having a pH in the range of 004 to 0.9, a pH in the range of 2.0 to 3.5 and a temperature in the range of 20 to 70 ° C is prepared, and the aqueous solution is treated with a galvanized steel sheet to obtain a galvanized steel sheet. Has filed an application for a method of manufacturing a zinc-based plated steel sheet having a Fe—Ni—O-based coating formed on the surface thereof (hereinafter referred to as Prior Art 5).

The prior art 5 is expected to have effects such as excellent press formability, spot weldability, adhesiveness and chemical conversion treatment, and can be supplied to consumers at low cost.

On the other hand, among galvanized steel sheets, particularly galvannealed steel sheets, they are often used in applications where the required level of appearance quality, such as outer panels of automobiles, is extremely severe due to their characteristics. In addition to the above characteristics, it is an essential requirement that the alloyed hot-dip galvanized steel sheet having the Fe-Ni-O-based coating formed thereon has good surface appearance and no defects such as flaws.

The present inventors have further studied an alloyed hot-dip galvanized steel sheet on which an Fe—Ni—O-based coating has been formed in order to satisfy the above demands of consumers.
When the amount of the -Ni-O-based coating is out of the predetermined range, the surface appearance is deteriorated, and it may be difficult to find a defect such as a fine flaw.

Further, when the Fe—Ni—O-based coating is formed to have a predetermined adhesion amount, it is difficult to obtain an appropriate adhesion amount due to a large variation due to the galvannealed steel sheet.

The present invention has been accomplished on the basis of the above-described studies. The present invention forms an appropriate amount of an Fe--Ni--O-based coating film to obtain press formability, spot weldability, adhesion, and chemical conversion. It is an object of the present invention to provide a method for producing a highly lubricated alloyed hot-dip galvanized steel sheet having excellent processability, surface appearance, and ease of finding defects.

[0021]

Means for Solving the Problems The invention according to claim 1 is F
eCl ₂ and NiCl ₂ , and the Fe content (g / g
l) and the Ni content (g / l) to the ratio of the Fe content (g / l) in the range of 0.004 to 0.9,
Is in the range of 2.0 to 3.5 and the temperature is in the range of 20 to 70 ° C., and a galvannealed steel sheet having an alloying degree (Fe%) of 8 to 12% is immersed in the aqueous solution. The immersion treatment time t (second) is adjusted according to the degree of alloying (Fe%), so that the surface of the plating layer of the alloyed hot-dip galvanized steel sheet has F
10-550 mg / m of e-Ni-O-based coating per side
^2. A method for producing a highly lubricated alloyed hot-dip galvanized steel sheet characterized by being formed in the range of ² .

[0022]

Next, the manufacturing conditions of the present invention will be described based on the above-mentioned reasons for limitation. In the present invention, the surface of the plating layer of the galvannealed steel sheet is made of Fe-Ni-O
The aqueous solution containing FeCl ₂ and NiCl ₂ was selected as the aqueous solution used for forming the system coating (hereinafter referred to as the coating treatment solution) because the use of chloride as the metal salt has high displacement precipitation efficiency. is there.

That is, when compared with nitrate and sulfate at the same salt concentration and the same treatment time, the metal salt of chloride is more Ni
This is because the adhesion amount of Fe and Fe is large, and the productivity is improved.

As a method for forming a Fe—Ni—O-based coating with a coating solution for a galvannealed steel sheet, a dipping method is employed to uniformly and uniformly form the Fe—Ni—O-based coating. Let it form.

F with respect to the sum of the Fe content (g / l) and the Ni content (g / l) in the coating solution used in the present invention.
e, by controlling the content (g / l) ratio within an appropriate range, the desired Fe can be deposited on the surface of the galvannealed steel sheet.
-A Ni-O-based coating can be formed. If the ratio Fe / (Fe + Ni) in the coating solution is less than 0.004, there is no effect of improving the adhesiveness, while the ratio Fe / (Fe +
If Ni) exceeds 0.9, the effect of improving spot weldability is reduced.

Therefore, Fe / (Fe + N) in the coating solution
i) was in the range of 0.004 to 0.9. Further, by setting the pH in the coating solution to an appropriate range, a coating can be formed efficiently. When the pH is less than 2.0, the amount of generated hydrogen gas is extremely increased, so that the effect of substitution precipitation of Ni and Fe is reduced. At a certain salt concentration and a predetermined treatment time, the attached amount of Ni and Fe is reduced, and productivity is reduced. Lower.

Further, the coating film is mainly composed of Ni and Fe metals, and the effects of improving press formability, spot weldability and adhesiveness cannot be obtained.

Even when the pH is low, it is possible to increase the amount of Ni and Fe deposited per unit time by increasing the salt concentration, but this leads to an increase in the cost of the processing solution and an increase in sludge. Is not preferred.

On the other hand, when the pH exceeds 3.5, Fe in the coating solution is oxidized violently, and surface defects of the product due to sludge are easily generated, which is not preferable.

When the temperature of the coating solution is high, the rate of the substitution precipitation reaction is high, the deposition efficiency of Ni and Fe is good, and the productivity is improved.

When the temperature is lower than 20 ° C., the reaction rate is low, and the Ni required for improving the properties of the galvannealed steel sheet is reduced.
In addition, it takes a long time to secure the Fe adhesion amount, and the productivity is reduced. On the other hand, if the temperature exceeds 70 ° C., the deterioration of the coating solution is accelerated due to an increase in the amount of impurity ions mixed into the coating solution, and equipment for maintaining the coating solution at a high temperature and thermal energy , Which leads to an increase in manufacturing costs.

[0032] Fe-Ni-O based film according to the present invention should be formed in the range of the attached amount of ^{10mg / m 2 ~550mg / m 2} .

When the amount of adhesion is less than 10 mg / m ² , the effects of improving press formability, spot weldability and adhesiveness cannot be obtained, and when the amount of adhesion exceeds 550 mg / m ² ,
As shown in Examples described later, the surface appearance of the alloyed hot-dip galvanized steel sheet having the Fe-Ni-O-based coating formed thereon is poor,
Further, it is difficult to find a defect due to a minute flaw or the like.

When the adhesion amount exceeds 550 mg / m ² , there is a risk that defects of the alloyed hot-dip galvanized steel sheet may be overlooked and the defective product may flow out to the customer,
Further, there is a risk that a defect may be overlooked in the product manufacturing process of the customer, the value of the final product may be lost, and the customer may be greatly annoyed.

On the other hand, the degree of alloying (Fe%) of the galvannealed steel sheet is set in the range of 8% to 12%. If the degree of alloying (Fe%) is less than 8%, alloying is not yet developed, and uneven burning is likely to occur, and the flaking resistance is reduced.

If the degree of alloying (Fe%) exceeds 12%, powder links are likely to occur during press forming.

On the other hand, when the amount of the Fe—Ni—O-based
To form a range of ^{0mg / m 2 ~550mg / m 2} , when treated by immersing the coating treatment solution galvannealed steel sheet in certain conditions, the adhesion amount of Fe-Ni-O based film is Very large variation.

FIG. 1 shows the degree of alloying (Fe) of the galvannealed steel sheet on which the Fe—Ni—O-based coating was formed.
%) And the amount of Ni attached to the Fe—Ni—O-based coating (mg / m
It is a figure which shows the relationship of ² ).

The conditions of the immersion treatment in the coating solution are as follows. As is clear from FIG. 1, the degree of alloying of the plating layer (Fe
%), The amount of Ni attached (mg / m ² ) in the Fe—Ni—O-based coating decreases. In the region A where the degree of alloying (Fe%) is small, the plating layer is mainly formed of the ξ phase, and in the region B where the degree of alloying (Fe%) is large, δ
It is formed mainly of one phase. It is considered that this variation in the adhesion amount is caused by the phase composition.

Accordingly, when an alloyed hot-dip galvanized steel sheet having an alloying degree of 8% to 12% is immersed in a coating solution under a certain condition and treated, the Fe—Ni—O alloy may be used depending on the degree of alloying.
Ni adhesion amount (mg / m ² ) in the system coating is about 100 mg /
There is a risk that m ^{2 will} also vary. The adhesion amount of the Fe—Ni—O-based coating is expressed by the Ni adhesion amount (mg
/ M ² ).

In the present invention, the degree of alloying (Fe
%), The immersion treatment time t (second) is adjusted to
-About 10 mg / m < ² > -550m about Ni-O type | system | group coating film
It is for forming a predetermined coating amount in the range of g / m ² .

In the present invention, as shown in FIG. 2, the amount of Fe—Ni—O-based film deposited (the amount of Ni deposited) when the degree of alloying (Fe%) was changed in the range of 8 to 12% was experimentally shown in FIG. Display) and the processing time.

By preparing a table as shown in FIG. 2 in advance, it is possible to obtain a necessary processing time and form a film. As an empirical formula, the relationship between the magnitude of the degree of alloying (Fe%) of the alloyed hot-dip galvanized steel sheet and the immersion time (seconds) was determined by using CW as the amount of the Fe—Ni—O-based coating in mg / m 2. ^When it is set to ² , it can be represented by the relational expression (1).

CW = {[a (Fe) + b] t + [c (Fe) + d] t} ² } (1) where F: alloying degree of alloyed hot-dip galvanized steel sheet (Fe
%) T: immersion treatment time (seconds) a, b, c, d: Coefficients and the following values were used.

A: -0.16, b: 2.54, c: -0.12
, D: 19.9 The CW is set by the equation (1), and the F is determined, so that the immersion processing time (second) is calculated. As a result, the processing time calculated for the alloyed hot-dip galvanized steel sheet as a coating solution (
Seconds) By immersion, the adhesion amount of a predetermined Fe—Ni—O-based coating can be obtained.

[0046]

The present invention will be further described below with reference to examples.

Table 1 shows a region A where the degree of alloying (Fe%) is small.
Degree of alloying (Fe%) of the alloyed hot-dip coated steel sheet, the surface alloy phase, and the coating weight (g /
m ² ), immersion time, Fe—Ni—O-based film adhesion amount (target value), Fe / (Fe +
Ni) and pH.

[0048]

[Table 1]

Table 2 shows the region B in which the degree of alloying (Fe%) is large.
Of alloyed hot-dip coated steel sheet (Fe%), surface alloy phase, coating weight (g / m ² ), immersion time, Fe—Ni—O-based coating Adhesion amount, Fe / (Fe + N) in Fe-Ni-O-based coating solution
i) indicates the pH.

[0050]

[Table 2]

F obtained under the conditions of Tables 1 and 2
For the alloyed hot-dip galvanized steel sheet on which the e-Ni-O-based coating was formed, the amount of the Fe-Ni-O-based coating and the properties such as press formability, spot weldability, adhesion, chemical conversion treatment, and surface appearance were evaluated. Blackness (L value), defect findability,
These evaluations were made based on the criteria in Table 5, and the results are shown in Tables 3 and 4.

In Tables 1 to 4, No. 8, No. 9 and N
o.10 is a comparative example.

[0053]

[Table 3]

[0054]

[Table 4]

[0055]

[Table 5]

The evaluation based on the criteria in Table 5 is as follows:
If there was an X mark, it was regarded as a comprehensive evaluation. The test method in the above example is as follows.

(1) Press Formability A coefficient of friction μ between a sample and a bead was calculated by a friction coefficient measuring apparatus according to the formula: μ = F / N. F is the sliding resistance,
N is the pressing load of the bead on the sample.

(2) Spot weldability and spot weldability were evaluated by the number of continuous spots in spot welding.

(3) Evaluation of Adhesiveness and Adhesiveness After the surfaces of the two samples were stuck together with an adhesive, they were evaluated by the peel strength when they were peeled off.

(4) Chemical conversion processability The chemical conversion processability was evaluated by microscopic observation of the crystal state of the zinc phosphate coating.

(5) Blackness (L value) as surface appearance Using a color tone meter, standard light was applied to the sample surface, the color tone was measured with a color camera, and the L value was calculated by calculation.

(6) Easiness of finding defects, The result of visual inspection of the surface after stopping the steel plate on the output side inspection table of the continuous hot-dip galvanizing equipment, and the grinding stone using the cut plate sample collected at the same position in the longitudinal direction of the steel plate The results were compared with the results of a running test. Specifically, evaluation was made based on the coincidence rate of the number of occurrences (found) of dross defects and indentations, which are typical defects of continuous hot-dip galvanizing equipment.

As is clear from Tables 3 and 4, in the examples, the immersion time (second) corresponding to the measured value of the degree of alloying (Fe%) was set for the target amount of coating film. Thereby, an accurate coating amount can be formed.

As shown in Comparative Examples No. 8 and No. 9 in Table 3, especially on the upper limit side of the coating amount which affects the surface characteristics, it depends on the immersion time (seconds), and the L value and the ease of finding defects can be improved. The evaluation was marked with a triangle.

In Comparative Example No. 10 in Table 4, the lower limit of the coating amount was affected by the immersion time (seconds),
Weldability and adhesiveness were marked with x.

As shown in Tables 3 and 4, good results were obtained for each characteristic in the examples of the present invention.

[0067]

As described above, according to the present invention, Fe-N
High lubricity alloyed hot-dip galvanizing with excellent press formability, spot weldability, adhesiveness and chemical conversion treatment properties, as well as excellent surface appearance and easy defect detection by forming an appropriate amount of i-O based coating Steel sheet can be obtained stably.

[Brief description of the drawings]

FIG. 1 shows the degree of alloying (Fe%) of a plated layer of an alloyed hot-dip galvanized steel sheet having a Fe—Ni—O-based coating formed on the premise of the present invention and the amount of Ni attached to the Fe—Ni—O-based coating. (M
g / m ² ).

FIG. 2 shows the degree of alloying (Fe%) according to the embodiment of the present invention.
Is changed in the range of 8 to 12%.
4 is a graph showing a relationship between a system coating amount (indicated by Ni amount) and a processing time.

[Explanation of symbols]

A A region mainly composed of a ξ phase having a small degree of alloying (Fe%) B A region mainly composed of a δ1 phase having a large degree of alloying (Fe%)

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor: Ritsutaka Sakurai 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) References JP-A-9-228020 (JP, A) JP-A Heihei 9-263965 (JP, A) JP-A-9-263964 (JP, A) International Publication 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 (1)

(57) [Claims] 1. The method according to claim 1, which comprises FeCl ₂ and NiCl ₂ ,
The ratio of the Fe content (g / l) to the sum of the e content (g / l) and the Ni content (g / l) is in the range of 0.004 to 0.9, and the pH is in the range of 2.0 to 3.5. And the temperature is 20 ~
Prepare an aqueous solution in the range of 70 ° C and determine the degree of alloying (Fe%)
8 to 12% of an alloyed hot-dip galvanized steel sheet is immersed in the aqueous solution, and the immersion time t (second) is adjusted in accordance with the degree of alloying (Fe%) to form a galvannealed steel sheet. Fe-Ni-O-based coating on the surface of the layer
A method for producing a highly lubricated alloyed hot-dip galvanized steel sheet, which is formed in a range of 550 mg / m ² .