JP4122643B2 - Alloyed hot-dip galvanized steel sheet with excellent sliding properties during press forming and press-forming method of alloyed hot-dip galvanized steel sheet - Google Patents

Description

【００２０】
本発明例は比較例に比べて成形余裕量が大きく、成形性に優れている。
【００２１】
【発明の効果】
以上のように、本発明によれば、合金化溶融亜鉛めっき鋼板の合金めっき最上層をζ相、その下層をδ₁相とし、ζとδ₁相のＸ線回折ピーク比（ζ／δ₁）を0.01≦（ζ／δ₁）≦0.25としかつP系,S系の極圧添加剤を１種以上含む潤滑剤を使用してプレス成形するように構成したので、摺動特性が向上し成形性に優れる。
【図面の簡単な説明】
【図１】摺動特性に及ぼすζとδ₁相のＸ線回折ピーク比（ζ／δ₁）と潤滑材中のP系,S系の極圧添加剤の有無の影響の一例を示す図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an alloyed hot-dip galvanized steel sheet excellent in press formability.
[0002]
[Prior art]
Iron-zinc alloyed hot-dip galvanized steel sheets are widely used mainly for steel sheets for automobiles because they are excellent in corrosion resistance and electrodeposition coating properties and are low in production costs. However, the conventional iron-zinc alloyed hot-dip galvanized steel sheet has inferior sliding characteristics as compared with the non-plated material, and the formability is hindered.
[0003]
In order to solve the above problem, conventionally, press molding is performed using a lubricant containing an extreme pressure additive, and for example, in JP-A-1-68456, there is no η, ζ phase on the surface layer, and δ ₁ In JP-A-2-175004, the surface of the plating film is adjusted to a predetermined roughness pattern at the time of skin pass rolling. In JP-A-2-185959, the roughness of the plating base material is determined by a skin pass. It is said that the sliding characteristics are improved by adjusting the roughness. Also, JP-A-2-258963, JP-A-3-249182 and the like are methods for coating the plating surface with oxides such as Zn, Mn and P, and JP-A-3-287782 is an organic resin film on the plating surface. In Japanese Patent Laid-Open No. 6-116746, improvement of sliding properties by surface modification such as a method of coating a metal oxide such as Ni is proposed.
[0004]
[Problems to be solved by the invention]
However, a method of using the oil containing the extreme pressure additive, the surface layer eta, there is no ζ phase, a method for the [delta] ₁ phase, the rough adjustment of the plated surface and plating the base metal, sufficient sliding characteristics Is not obtained, and molding defects occur. Further, the surface modification method can increase the manufacturing cost although sufficient sliding characteristics can be obtained. Under such circumstances, there is a strong demand for the development of an inexpensive alloyed hot-dip galvanized steel sheet having sufficient sliding characteristics.
[0005]
An object of the present invention is to provide an alloyed hot-dip galvanized steel sheet and a press-forming method of the alloyed hot-dip galvanized steel sheet that solve the above-mentioned problems.
[0006]
[Means for Solving the Problems]
In a first invention for solving the above problems, the uppermost layer of the alloy plating is a ζ phase and the lower layer is a δ ₁ phase, and the X-ray diffraction peak ratio ζ / δ _{1 of} ζ and δ ₁ phase is 0.01 ≦ ζ / An alloyed hot-dip galvanized steel sheet having excellent sliding characteristics at the time of press forming , in which δ ₁ ≦ 0.25 and a lubricant containing at least one P-type or S- type extreme pressure additive is applied.
[0007]
In addition, the second aspect of the invention is that the uppermost layer of the alloy plating is the ζ phase and the lower layer is the δ ₁ phase for use in which a lubricant containing at least one P-type or S- type extreme pressure additive is used during press working. Thus, the alloyed hot-dip galvanized steel sheet having excellent sliding properties during press forming , in which the X-ray diffraction peak ratio ζ / δ _{1 of} the ζ and δ ₁ phases is 0.01 ≦ ζ / δ ₁ ≦ 0.25.
The third invention alloy plating uppermost zeta phase, the lower layer consists of [delta] ₁ phase, the zeta and [delta] _1-phase X-ray diffraction peak ratio zeta / [delta] ₁ of a 0.01 ≦ ζ / δ ₁ ≦ 0.25 Alloy This is a press forming method of an alloyed hot dip galvanized steel sheet, characterized in that the hot dip galvanized steel sheet is press formed using a lubricant containing at least one P- type or S- type extreme pressure additive.
[0008]
Incidentally, zeta and [delta] _1-phase X-ray diffraction peak ratio zeta / [delta] ₁ of the ratio of the measured zeta and [delta] ₁ Phase respective X-ray diffraction peak intensity in the coating layer was at the same time.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The P-type and S- type extreme pressure additives have a large effect of suppressing adhesion to the tool with respect to the ζ phase, and have no effect on the δ ₁ phase. Therefore P system, in the state where the lubricant containing more than one kind of S-based extreme-pressure additive is present, the frictional force of the ζ phase is smaller than the frictional force [delta] ₁ phase. However, P based, in sliding in the absence of lubricants and lubricants containing no S-based extreme-pressure additives, friction ζ phase significantly greater than the frictional force [delta] ₁ phase. In sliding in press molding, the lubricant that exists between the material and the tool decreases due to intermittent contact between the material and the tool due to sliding, and the lubricant is not present locally. At the same time, the plating surface is scraped away from the upper layer.
[0010]
In the present invention, a phase structure in which there are thin zeta phase structure of the alloy plating layer to [delta] _1-phase upper, a range X-ray diffraction peak ratio of zeta and [delta] ₁ phase is 0.01 ≦ ζ / δ ₁ ≦ 0.25 By doing so, there is a lubricant containing one or more P-type and S- type extreme pressure additives on the surface of the plated steel sheet at the start of press forming, and while the lubricant can exist between the material and the tool, Excellent sliding due to the plating film structure that the surface is the ζ phase, the lubricant is reduced by sliding, the ζ phase is worn, and the δ ₁ phase appears on the outermost layer from the time the lubricant disappears Characteristics are obtained.
[0011]
In the present invention, the X-ray diffraction peak ratio ζ / δ ₁ between the ζ and δ ₁ phases is limited to 0.01 ≦ ζ / δ ₁ ≦ 0.25. In the range of 0.01> ζ / δ ₁ , the outermost ζ phase is insufficient. However, the extreme pressure additive does not act effectively, and in the range of ζ / δ ₁ > 0.25, the outermost ζ phase is excessive, and the steel plate is not present at the contact point between the steel plate and the tool. This is because since the ζ phase is present in the outermost layer, the friction coefficient increases, the sliding resistance increases, and the press formability decreases.
[0012]
【Example】
Next, examples of the present invention are shown together with comparative examples.
[0013]
(Example 1)
As a plating base material, an ultra-low carbon cold-rolled steel sheet with a thickness of 0.7 mm and a tensile strength of 270,340,440 MPa, a low-carbon cold-rolled steel sheet with a thickness of 1.4 mm and a tensile strength of 440,590 MPa, a thickness of 1.6 mm, and a tensile strength of 440,590 MPa Inductive heating type alloying furnace immediately after plating with 30 to 90 g / m ² (per side) in a zinc bath containing Al: 0.08 to 0.14 wt% The alloying treatment was carried out under the condition that the furnace outlet side plate temperature was 450 to 600 ° C. to produce an alloyed hot-dip galvanized steel sheet. The plating phase structure was changed by appropriately selecting an alloying furnace heating pattern.
[0014]
The friction coefficient (flat plate sliding friction coefficient) of the steel plate obtained above was measured, and the sliding characteristics were evaluated. The coefficient of friction is measured when the steel plate is degreased with solvent and applied with lubricant containing P or S extreme pressure additive, or with lubricant without P or S extreme pressure additive. The dimensions were 10 mm wide × 10 mm long, and the tool was subjected to quenching and tempering treatment of material SKD11 at a pressing surface pressure of 5 kgf / mm ² and a sliding speed of 1 m / min.
[0015]
X-ray diffraction peak ratio of zeta and [delta] _1-phase in Figure 1 zeta / [delta] ₁ and showing the relationship of the flat sliding friction coefficient. A steel sheet having a low friction coefficient is obtained in the range of 0.01 ≦ ζ / δ ₁ ≦ 0.25, which is the range of the present invention. This is because, as described above, the phase structure has an appropriate amount of ζ phase on the δ ₁ phase. On the other hand, in the range of 0.01> ζ / δ ₁ , the outermost surface ζ phase is insufficient, and the extreme pressure additive does not act effectively, and in the range of ζ / δ ₁ > 0.25, the outermost surface ζ phase is excessive. Even after the lubricant is no longer present at the contact point between the material and the tool, the friction coefficient is high because the ζ phase exists in the outermost layer of the steel sheet.
[0016]
(Example 2)
An ultra-low carbon cold rolled steel sheet with a thickness of 0.7mm and a tensile strength of 270MPa is used as the plating base material, and the coating amount is 45g / m ² (per side) in a zinc bath containing Al: 0.10wt%. Immediately after that, an alloying treatment was performed in an induction heating type alloying furnace under the condition that the furnace outlet side plate temperature was 450 to 600 ° C., and four different alloyed hot dip galvanized steel sheets A to ζ / δ ₁ D was manufactured. The plating phase structure was changed by appropriately selecting an alloying furnace heating pattern.
[0017]
These four types of steel plates A to D were formed with an actual part scale front fender mold, and formability was evaluated. Formability was evaluated by applying a lubricant containing P-type and S-type extreme pressure additives and a lubricant containing no P-type and S-type extreme pressure additives after alkaline degreasing of the steel sheet. The case was evaluated and the molding allowance = (cushion force at the limit of crack generation) − (wrinkle generation limit cushion force) was evaluated.
[0018]
Table 1 shows the mechanical property values of the four types of steel sheets subjected to formability evaluation, the phase structure (ζ / δ ₁ ) of the plating layer, and the presence or absence of an extreme pressure additive in the lubricating oil. As shown in Table 1, the mechanical properties of the four types of steel plates are equivalent. Table 1 also shows the evaluation results of formability.
[0019]
[Table 1]

[0020]
The inventive example has a larger molding allowance than the comparative example and is excellent in moldability.
[0021]
【The invention's effect】
As described above, according to the present invention, the uppermost layer of the alloyed hot-dip galvanized steel sheet is the ζ phase and the lower layer is the δ ₁ phase, and the X-ray diffraction peak ratio (ζ / δ _{1) of} ζ and δ ₁ phase. ) and _{0.01 ≦ (ζ / δ 1)} ≦ 0.25 Toshikatsu P system, than was configured to press molding using a lubricant containing S-based extreme-pressure additive one or more, improved sliding characteristics Excellent moldability.
[Brief description of the drawings]
FIG. 1 is a graph showing an example of the influence of the X-ray diffraction peak ratio (ζ / δ ₁ ) of ζ and δ ₁ phases on the sliding characteristics and the presence or absence of P-type and S-type extreme pressure additives in the lubricant. .

Claims (3)

Alloy plating top layer zeta phase, the lower layer consists of [delta] ₁ phase, the zeta and [delta] _1-phase X-ray diffraction peak ratio zeta / [delta] ₁ of a _{0.01 ≦ ζ / δ 1 ≦ 0.25} , P type, S type excellent galvannealed steel sheet sliding property during press molding, characterized in that the coated extreme pressure additive lubricant containing one or more. The uppermost layer of the alloy plating is a ζ phase, and the lower layer is a δ ₁ phase, and the X-ray diffraction peak ratio ζ / δ _{1 of} ζ and δ ₁ phase is 0.01 ≦ ζ / δ ₁ ≦ 0.25, An alloyed hot-dip galvanized steel sheet with excellent sliding properties during press forming, using a lubricant containing one or more P-type and S- type extreme pressure additives. The uppermost layer of alloy plating is the ζ phase, and the lower layer is δ ₁ Ζ and δ ₁ X-ray diffraction peak ratio of phase ζ / δ ₁ But, 0.01 ≦ ζ / δ ₁ ≦ 0.25 Alloyed hot dip galvanized steel sheet, P system , S A press forming method for an alloyed hot-dip galvanized steel sheet, characterized by press forming using a lubricant containing at least one type of extreme pressure additive.

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