JPH07197226A - Zn-ni alloy plated steel sheet excellent in press formability and powdering resistance - Google Patents

Abstract

PURPOSE:To improve press formability and powdering resistance by providing plural annular recessed parts on the surface of a Zn-Ni alloy plated steel sheet, regulating the volume of the annular recessed parts to a specific quantity, and also regulating Ni content in a surface modified layer plating to a specific amount. CONSTITUTION:A Zn-Ni alloy plating 3 is formed on the surface of a matrix 4. Plural annular recessed parts 1 are provided. The sum of respective volumes of the recessed parts per square millimeter of the surface of a steel sheet, V, shown by V=SXhXn satisfies V=(0.7X10<6> to 8X10<6>)mum<3>. In this equation, when (b in the figure) means the recessed part width of the annular recessed part and (d in the figure) means the central diameter of the recessed part, S, (h), and (n) represent the cross-sectional area of the recessed part, the depth of the recessed part, and the number of the recessed parts per square millimeter of the surface of the steel sheet, respectively. A surface modified layer 2 is provided. The average Ni content in the whole plating is regulated to 9-15wt.%, and the Ni content in the surface layer 2 is also regulated so that it is 1.01 to 1.75 times the average Ni content. By this method, press formability and powdering resistance can be improved without deteriorating the corrosion resistance inherent in the Zn-Ni alloy plating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has excellent press formability and powdering resistance, and is suitable for use as a surface-treated steel sheet for difficult-to-form products such as automobiles and home appliances.
The present invention relates to a Ni-based alloy plated steel sheet.

[0002]

2. Description of the Related Art A wide variety of surface-treated steel sheets are used as measures against corrosion of automobile bodies by sprayed rock salt for preventing road freezing in winter in cold regions. Galvanized steel sheets are listed as the simplest surface-treated steel sheets, but high corrosion resistance is required for automotive applications, so it is necessary to increase the amount of plating, which causes problems such as weldability and workability at the vehicle body assembly stage. . Therefore, many alloy platings have been proposed that have high corrosion resistance even if the plating amount is thin.
Zn-based alloy plating containing an iron group metal such as e, Co, or Ni as an alloy component has been found to have good corrosion resistance as well as weldability and workability, and is widely used.

On the other hand, automobiles and home electric appliances are required to have higher and more versatile formability in accordance with the diversification of needs, and various types can be obtained by the material design technology utilizing the component design and rolling and annealing conditions. A steel sheet having the forming characteristics of is developed. However, in the case of a plated steel sheet, even if a plating film is simply applied on a steel sheet that is excellent in forming, the physical properties of the steel sheet that is the base material and the plating film are significantly different, so the forming characteristics of the steel sheet itself may differ in the actual forming stage. It may not be fully exerted. This is because the surface that actually contacts the press die becomes a plating film and the effect of its characteristics increases.
When attempting to apply a plated steel sheet to a difficult-to-form product that requires deep drawing or a complicated shape, unexpected forming defects such as cracks and mold galling are likely to occur. To solve such a problem, as disclosed in JP-A-2-274853-6, a technique for improving the formability by adjusting the roughness of the steel sheet surface in advance in an alloyed hot-dip galvanized steel sheet, and JP-A-4-27453. As disclosed in JP-A-214877, a technique for imparting an inorganic compound to the surface of a zinc-plated steel sheet to improve slidability is disclosed, but none of them has reached a satisfactory level.

[0004]

As described above, Zn-based alloy-plated steel sheets have excellent corrosion resistance, but their applications are limited in terms of press formability and are not fully utilized at present. . In particular, Zn-Ni alloy-plated steel sheets are thin and have excellent corrosion resistance, so that there is a great need for expanding applications to automobiles and home appliances, and improvement in press formability is desired. INDUSTRIAL APPLICABILITY The present invention is a Zn-N which can satisfy high press-moldability and powdering resistance mainly for automobiles and home appliances.
It is an object to provide an i-based alloy plated steel sheet.

[0005]

[Means for Solving the Problems] Zn-Ni alloy plating
By providing multiple ring-shaped recesses on the steel plate surface,
The cross-sectional area of the recess, where b is the width of the recess and d is the center diameter of the recess
S, recess depth h, steel plate surface 1 mm² Number of recesses per hit
Where n is, the steel plate surface is 1 mm² The total volume V of the recess
Is represented by V = S × h × n, and V is 0.7 × 10.⁶μm³ ~
8 x 10⁶μm ³ And the average Ni content of the total plating thickness is satisfied.
The content is 9 to 15% by weight, and the Ni content of the surface layer
Is 1.01 to 1.75 times the average Ni content, Zn-
Having Ni alloy plating layer on both sides or one side of steel sheet
Press moldability and powdering resistance
Excellent Zn-Ni alloy plated steel sheet.

[0006]

The Zn-Ni alloy plated steel sheet excellent in press formability and powdering resistance of the present invention is provided with a plurality of ring-shaped recesses on the plated surface and the recessed volume is 1 mm ²
And per 0.8~7.5 × 10 ⁶ μm ^3, an average content of Ni which is a main component of the alloy is 9-15 wt%, high eyes Ni content of the surface layer is than the average Ni content It is characterized in that it has been modified to become. As a method for modifying the plating film, a method of preferentially dissolving Zn on the plating surface by dipping in a weakly acidic aqueous solution or anodic electrolysis after applying Zn—Ni alloy plating, and plating with a high Ni content on the plating surface are used. The former method is more advantageous in terms of stability and economic efficiency.

The present invention will be described in detail below with reference to the drawings. FIG. 1 schematically shows a vertical cross section of one side of a plated steel sheet according to the present invention, wherein reference numeral 2 is a surface reforming layer, and 3 is Z.
n-Ni type alloy plating layer, 4 shows base iron. Further, FIG. 2 schematically shows the plane of the surface of the plated steel sheet with respect to the arrangement of the recesses 1 in FIG. 1, and reference numeral 5 denotes a Zn—Ni alloy plated steel sheet. Therefore, first, the research results up to the present invention will be described.

3 to 5 show the test results of the press formability and powdering resistance of Zn-Ni alloy plated steel sheets. The test method is as follows. A Ti-added ultra-low carbon steel was used as a plating base plate, and a ring-shaped recess was formed on the surface of the steel plate by pressure control. The Zn-Ni plating adhesion amount was 20 g / m ² , and the Ni content was 5-20 wt% Zn-Ni. The alloy was plated and subjected to a press formability test.

The press formability test is evaluated by a punch diameter of 50.
mm, draw ratio 2.2, apply low viscosity oil and perform 10 cylindrical press forming continuously, and give a rating of 1 to 5 according to cracking, punch load, and powdering degree by side wall taping of the pressed product. went. A rating of 3 or higher was evaluated as having no practical problem. 5: There is no crack and the punch load is almost at the original plate level. No powdering occurred. 4: There is no crack and the punch load is slightly higher than the original plate. The powdering is very small. 3: There is no crack and the punch load is considerably higher than the original plate. There is a lot of powdering. 2: 6 or less cracks. There is a lot of powdering. 1: 7 or more cracks. There is a lot of powdering.

The research results will be described below along with the history of the research. First, the effect of the Ni content on the press formability was quantitatively grasped, and an examination was conducted. The results are shown in FIG. This formability test is based on the coating weight of 2
0 g / m ² , the volume of the ring-shaped recess is ^{2 to} 5 per 1 mm 2.
It was carried out under the conditions of × 10 ⁶ μm ³ and without modifying the plating film.

Referring to FIG. 3, the press formability depends on the Ni content, and if the Ni content is less than 9%, the plating layer is soft and the adhesion with the tool becomes strong, so that the friction resistance increases and cracks occur. Further, if the Ni content exceeds 15%, the formability is good, but since powdering increases, push defects are likely to occur, which is not preferable. With Ni of 9 to 15%, the punch load is higher than that of the original plate, but since there is no crack, there is no practical problem. From this result, the influence of the volume of the ring-shaped recess was examined next, and the result is shown in FIG. This formability test was performed under the conditions that the coating amount was 20 g / m ² , the Ni content was 9 to 15%, and the plating film was not modified.

FIG. 4 shows the relationship between the volume of ring-shaped recesses on the surface of a Zn-Ni alloy plated steel sheet and press formability. Referring to FIG. 4, the press formability depends on the volume of the ring-shaped recess on the plating surface, and the volume of the recess per 1 mm ^{2 of} the plating surface is preferably in the range of 0.7 to 8 × 10 ⁶ μm ³ . The volume of the recesses per 1 mm ^{2 of the} plating surface is set to 0.7 × 10 ⁶ μm ³ or more because if the volume is less than that, the lubricant is less secured and the effect on the formability and die galling is small. The reason why the particle size is set to 10 ⁶ μm ³ or less is not preferable because the number of protrusions is larger than that, and a plating flaw is generated due to the generation of plating powder due to damage of the protrusion.

Next, the most important feature of the present invention is the modification of the surface layer.
Explain the quality effect. Figure 5 shows the amount of plating film deposited
20 g / m² , The average Ni content is 9 to 15% by weight,
The volume of the ring-shaped recess on the surface is 0.7 × 10⁶μm³~
8 x 10⁶μm³Ni% (Ni_S)When
Average Ni% of total plating thickness (Ni_B) Ratio (Ni_P) And success
The relationship of formality is shown. Referring to FIG. 5, the formability is Ni._P
Is preferably in the range of 1.01 to 1.75. Ni _P1.01
The above is less than that, the hardening of the plating surface layer increases
Is small and the effect of moldability is small, and is 1.75 or less.
The reason is that if it exceeds that value, moldability is good, but powdering increases.
In addition, it is not preferable. A more preferable range is the surface layer
Ni_PIs 1.1 to 1.5 times.

The object of the present invention is that the average Ni content is 9 to 1.
It is 5% by weight and is a Zn-Ni alloy-plated steel sheet having the above-mentioned modified surface layer, and in addition to Zn and Ni as plating components, for example, Co, Fe, Mn, Cr,
Metals such as Pb and Sn; SiO ₂ , Al ₂ O ₃ and BaC
Inorganic compounds having poor solubility such as rO ₄ ; or those containing one or more organic compounds are included. The total content of components other than Ni is preferably 5% by weight or less, and within this range, the effects of the present invention are exhibited without any trouble. In the present invention, the coating amount is not particularly limited, but from the viewpoint of corrosion resistance and manufacturing cost, it is 10 to 60 g / m ^2.
Is a practical range.

The Zn-Ni alloy plating film having the modified surface layer as in the present invention may be formed on only one side or both sides of the steel sheet and can be appropriately selected according to the object to be formed. When the present invention is used for automobiles and home appliances,
A steel plate thickness of 0.4 mm to 1.2 mm is suitable.

[0016]

As described above, according to the present invention, the Zn--Ni
By providing a ring-shaped recess on the surface of the base alloy-plated steel sheet and further modifying the surface layer to have a high Ni content, Zn
-It has succeeded in improving press formability and powdering resistance without impairing the excellent corrosion resistance originally possessed by Ni-based alloy plating. It can be expanded to difficult-to-form parts, etc., and is of great practical value industrially.

[Brief description of drawings]

FIG. 1 is a longitudinal section of a Zn—Ni alloy plated steel sheet according to the present invention,

FIG. 2 is a diagram showing an example of an array of ring-shaped recesses in FIG.

FIG. 3 is a diagram showing the relationship between the average Ni content of Zn-Ni alloy plated steel sheet and press formability.

FIG. 4 is a diagram showing the relationship between the surface recessed volume of a Zn—Ni alloy plated steel sheet and press formability.

FIG. 5: Ni% of the surface layer portion of a Zn-Ni alloy plated steel sheet
It is a diagram showing the relationship between the molding against (Ni _S) and the average Ni% of the total plating thickness ratio _{(Ni B) (Ni P)} .

[Explanation of symbols]

1 Ring-shaped recessed part of the plated steel sheet according to the present invention 2 Surface modified layer 3 Zn-Ni alloy plated layer 4 Base iron 5 Zn-Ni alloy plated steel sheet b Recess width d Recess center diameter h Recess depth t Plated steel sheet Thickness of the plate S Cross-sectional area of the recess of the plated steel sheet P ₁ Center distance between recesses adjacent to the rolling direction of the plated steel sheet P ₂ Center distance between rows in the rolling direction of the plated steel sheet

Front page continuation (72) Inventor Fumio Yamazaki 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corp. Kimitsu Steel Co., Ltd.

Claims (1)

[Claims] 1. A Zn-Ni alloy-plated steel sheet surface is provided with a plurality of ring-shaped recesses, the recess width of the ring-shaped recess is b, and the recess diameter is S, the recess cross-sectional area is S, and the recess depth is Where h is the height and n is the number of recesses per 1 mm ^{2 of} the steel plate surface, the total volume V of recesses per 1 mm ^{2 of} the steel plate surface is V = S ×
V represented by h × n is 0.7 × 10 ⁶ μm ³ to 8 × 10 ^6.
μm ³ is satisfied, and the average Ni content in the entire plating thickness is 9 to
15% by weight and the Ni content of the surface layer is average Ni
Z having excellent press formability and powdering resistance, characterized in that it has a Zn-Ni alloy plating layer 1.01 to 1.75 times the content on both sides or one side of the steel sheet.
n-Ni alloy plated steel sheet.