JPS624858A - Hot dip galvanized steel sheet having superior adhesion and workability and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a hot dip galvanized steel sheet having superior adhesion and workability by hot dip galvanizing the surface of a steel sheet in a hot dip galvanizing bath having a specified composition and by heating the resulting Zn layer to form a Zn-Fe alloy layer of a specified thickness. CONSTITUTION:The cleaned surface of a steel sheet is hot dip galvanized in a hot dip galvanizing bath contg. <0.1% Pb and 0.05-0.25% Al at 440-500 deg.C to form a Zn layer of 4-25mum thickness. The hot dip galvanized steel sheet is heated to 420-600 deg.C to alloy the lower part of the Zn layer contacting with the steel sheet 1 with Fe in the steel sheet. By the alloying, a Zn-Fe alloy layer 2 is formed and a Zn layer 3 is left on the surface of the layer 2. At this time, the thickness of the Zn-Fe alloy layer 2 is regulated to 1/4-3/4 of the total thickness of the layers 2, 3. A hot dip galvanized steel sheet having superior adhesion and not causing stripping by press working is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hot-dip galvanized steel sheet with excellent adhesiveness and workability, and a method for manufacturing the same.

(Prior Art and Problems) Hot-dip galvanized steel sheets are widely used as corrosion-resistant steel sheets by automobile manufacturers and the like, but welding is being replaced by adhesive bonding for joining steel sheets. In addition, workability has become even more severe, and there is a demand for hot-dip galvanized steel sheets with excellent workability, that is, galvanized steel sheets that do not peel off the plating even during severe press working.

However, no conventional galvanized steel sheet has excellent adhesive properties.

Technology (invention) as disclosed in Japanese Patent Application Laid-open No. 59-67358
has been disclosed, but this has excellent weldability and is used differently from the present invention.

(Object of the Invention) The present invention has been made to solve the above-mentioned problems, and provides a hot-dip galvanized steel sheet with excellent adhesiveness and workability, and a method for manufacturing the same.

(Means for Solving the Problems) The gist of the present invention to achieve the above object is to set the total plating layer thickness of the galvanized steel sheet (total thickness of the zinc layer and alloy layer to 4 to 25 μm, and to A hot-dip galvanized steel sheet with excellent adhesion and workability, characterized in that the thickness of the alloy layer in the plating layer is much larger than the total thickness of the plating layer, and a zinc layer is formed on the alloy layer; and Plating composition pbo, i% or less, At0
．． 440 consisting of 05-0.25%, residual impurities and Zn
The steel plate is introduced into a ~500C plating bath, and the plating thickness is 4.
The plated steel plate is controlled to ~25μm and then plated at a temperature of 420~
Adhesion and workability characterized by heating at 600°C and configuring the alloy layer thickness in the total plating layer thickness (total layer thickness of zinc layer and alloy layer) to l/~- of the total plating layer thickness. This is an excellent method of manufacturing hot-dip galvanized steel sheets.

Next, details of the hot-dip galvanized steel sheet and the manufacturing method thereof according to the present invention will be described.

FIG. 1 shows a cross-sectional view of a hot-dip galvanized steel sheet according to the present invention. The plated steel sheet of the present invention is one in which an alloy layer 2 and a zinc layer 3 are sequentially formed on a steel sheet 1 as shown in the drawings, and such a plating layer is formed on one or both sides of the steel sheet.

That is, the steel plates of the present invention as described above can be firmly bonded by, for example, bonding them with an epoxy resin adhesive. The reason for this is that when the steel sheet of the present invention is manufactured by the method described above, PE diffusion from the steel sheet to the plating layer inevitably reaches a portion of the plating outermost surface. This is because the wettability of the adhesive is improved and the bond is made stronger.

Furthermore, when the hot-dip galvanized steel sheet according to the present invention is subjected to press working, the zinc on the surface of the galvanized steel sheet hardly adheres to the mold of the press machine.

The excellent effect of eliminating press flaws caused by adhesion of plated metal (zinc) to the mold can be obtained. The reason why there is almost no adhesion of plated metal to the mold is because, by manufacturing the steel plate of the present invention by the method described above, PE diffusion from the steel plate to the plated layer inevitably reaches the outermost surface of the plated part. This is because the surface friction resistance of the plated steel sheet becomes smaller.

Next, the total layer thickness of plating (total layer thickness of zinc layer and alloy layer R3
If it is less than 2 m, it will be difficult to function as a corrosion-resistant steel plate.
If the pain exceeds 5μ, the plating layer tends to peel off during press molding, which is not preferable.

Next, the manufacturing method is to reduce the PB content in the plating bath to 0.1% or less, but if it exceeds 0.1%, a snoggle pattern will occur and it will be difficult to obtain a beautiful surface. Undesirable.

In addition, At should be set at 0.05 to 0.25%, but 0
．． If it is less than 0.05%, the formation of the alloy layer will be rapid.

Adjustment of the alloy layer thickness 9 is industrially difficult due to the heating temperature and time as described below, which is not desirable.If it exceeds 0.25%, the formation of the alloy layer is delayed, and the alloy layer thickness is industrially difficult to adjust at the heating temperature and time as described below. becomes difficult to adjust.

The plating bath temperature is 440 to 500°C, but as mentioned above, the bath temperature is preferably within this range due to the fluidity of the plating metal, which adjusts the plating layer thickness to 4 to 25 μm. It is ℃. Under these conditions, the alloy layer thickness in the total plating layer (total thickness of zinc layer and alloy layer) is 1/~3/4 of the gold plating layer thickness (hereinafter abbreviated as alloy layer thickness ratio 1/~heat). ), the heating time is 10 to 60 seconds in the case of continuous treatment, for example. Also, the alloy layer referred to here has a pe content of 2.5 to 7.0%.
It is contained.

The plated steel sheet of the present invention is designed to have an alloy layer thickness ratio of l/~-, but if the heat treatment after plating is such that the alloy layer thickness ratio is less than -, the PE diffusion from the steel sheet will hardly reach the plating outermost surface. Therefore, it cannot be expected to improve the wettability of the adhesive or improve workability by reducing the frictional resistance of the plated surface.
Further, if heat treatment is performed after plating until the alloy layer thickness ratio exceeds 1, it is preferable from the viewpoint of preventing the plating from peeling off during press forming and also from the viewpoint of the appearance of the plated surface.Therefore, the plated steel sheet of the present invention is Adhesion and workability cannot be improved unless the lower layer is alloyed by hot-dip galvanizing and heating. For example, after hot-dip galvanizing, the entire plated layer is alloyed by heating, and then the upper layer is hot-dip galvanized or electrogalvanized, or an alloy layer.

If both the zinc layer and the zinc layer are electroplated, this effect cannot be obtained.

(Examples) Next, Table 1 shows Examples 1 to 6 of the present invention together with Comparative Examples 1 to 4.

In Table 1 above, Examples 1 to 6 and Comparative Examples 1 to 4 were carried out in the following manner.

Note 1 The plated original plate is O: 0.04%ss'5O-02%
, p: o, ozs% * M”: (L 25%, S:
0.015X, ht: o, os%, N: 0.0
05%.

Fe: A plate made of residual material and having a thickness of 0.8 cm was used.

Note 2 Adhesion is determined by applying epoxy resin to the surface of the plated steel plate.
- Coating, adhering the plated steel plate and pulling it until it peels off,
The degree of tensile strength at the time of peeling is indicated (O: strong, Δ: medium.

×: weak).

Note 3 Workability was determined by sandwiching the plated steel plate 6 between die 4゜5 with a pressing load of 400 kf, as shown in Figure 2.
was pulled for 400M, and the degree of adhesion of the plating metal to the die 4.5 was displayed (○: no adhesion, Δ: slight adhesion but no practical problem, ×: adhesion hole).

In FIG. 2, A-H indicates the following sizes.

A: 30■, B: 30■, O: 30meD: 5
0■, E: 3 liters, F: 3 liters.

G: 3B, H: 3 liters.

Note 4 In Comparative Example 3, after hot-dip galvanizing, the entire zinc layer was alloyed, and then a hot-dip galvanized layer was formed on top of it.

Note 5 In Comparative Example 4, both the alloy layer and the zinc layer were electroplated.

According to the present invention, galvanized steel sheets can be provided with adhesive properties, and conventional welding is not required, resulting in great technological innovation in industry. In addition, excellent effects can be obtained since workability (plating removal) can also be improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view of a plated steel sheet according to the present invention. FIG. 2 is an explanatory diagram showing an example of a peelability (workability) test of a plated steel plate. l... Steel plate, 2... Alloy layer, 3... Zinc layer, 4.
5...Dice, 6...Plated steel plate.

Claims (2)

[Claims] (1) The total plating layer thickness (total layer thickness of zinc layer and alloy layer) of the galvanized steel sheet is 4 to 25 μm, and the alloy layer thickness in the total plating layer thickness is 1/4 to 3/4 of the total plating layer thickness. A hot-dip galvanized steel sheet with excellent adhesion and workability, characterized by having a zinc layer formed on the alloy layer. (2) Plating bath composition Pb 0.1% or less, Al 0.05~
440-500 consisting of 0.25%, residual impurities and Zn
The steel plate is introduced into a plating bath at ℃, and the plating thickness is 4 to 25 μm.
The plated steel sheet is then heated to a plate temperature of 420 to 600°C to reduce the total plating layer thickness (total layer thickness of zinc layer and alloy layer).
A method for producing a hot-dip galvanized steel sheet with excellent adhesiveness and workability, characterized in that the thickness of the inner alloy layer is 1/4 to 3/4 of the total plating layer thickness.