JPH06116745A - Surface-treated steel sheet with excellent deep drawability, mold galling resistance, and corrosion resistance - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention provides deep drawability and mold galling resistance for easy and stable production of deep drawn parts used in automobiles, furniture, home appliances, etc. by press molding. To provide an excellent surface-treated steel sheet. [Structure] A plurality of staggered recesses are provided on the surface of the steel plate, and the depth of the recesses is 0.5 to 10% of the plate thickness.
The total cross-sectional area of ² per recess and 0.3 mm ² or more, and the total volume of the recess is 0.8 × 10 ⁶ μm ³ or more, 1.0 of the transfer length further recess distance refers largest recess As described above, a surface-treated steel sheet having excellent deep drawability and mold galling resistance can be easily and stably formed by applying an organic film over three layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface steel sheet which is excellent in deep drawability, die galling resistance and corrosion resistance when press-forming deep drawn parts used in automobiles, furniture, home appliances and the like.

[0002]

2. Description of the Related Art Conventionally, in forming deep-drawn parts such as oil vans for automobiles, bathtubs and sinks for furniture, and cartridge tanks for petroleum stoves for home appliances,
It is known that as the amount of processing increases, the temperature of the deep-drawing parts rises due to the heat generation of the processing, as well as the temperature of the press die due to the propagation of the heat generation of the processing. Looking at this temperature rise from the viewpoint of moldability, the number of moldings per unit time is comparatively small even when using a hydraulic press and a mechanical press in the past. It was rarely done.

However, since transfer presses have become widespread in recent years and have come to be applied to the molding of such deep-drawing parts as well, the influence of a rise in the mold temperature becomes extremely large, and the deep-drawability is lowered and die galling is caused. The problem of molding failure due to the occurrence has begun to emerge. For this reason, various measures have been taken against the deterioration of deep drawability due to the rise of the mold temperature and the defective moldability due to the occurrence of mold galling. For example, the method of applying water-soluble cooling oil to the entire mold is effective, but there is a problem that the cooling oil scatters around when pressing and the working environment deteriorates. Also, the use of lubricants containing extreme pressure additives Is effective, but the cost of degreasing after molding increases, and it is effective in the method of reducing deformation heat by increasing the number of drawing steps, but the manufacturing cost rises due to the increase in the number of molds etc. However, the actual situation is that the measures are not always satisfactory.

As a countermeasure against the occurrence of mold galling,
It is known that it is most effective to control the surface roughness of the steel sheet, and generally, increasing the roughness is advantageous for the occurrence of mold galling. However, if the roughness is large, the surface quality after coating is inferior, and a steel sheet that is effective against the occurrence of mold galling and is excellent in deep drawability is desired. As a prior art related to the present invention, Japanese Patent Laid-Open No. 62-16
There is Japanese Patent No. 8602, "Steel for coating and its manufacturing method". Its content is excellent in coating image clarity by regularly controlling the roughness, and does not mention the surface-treated steel sheet excellent in deep drawability and die galling resistance of the present invention, and suggests nothing. Does not give.

[0005]

As described above, in the case of forming a deep-drawn part in the conventional surface-treated steel sheet, the temperature of the part and the mold rises due to the heat generated during processing, and the performance of the lubricant deteriorates due to the temperature rise. As a result, there is a serious problem that molding is defective due to a decrease in deep drawability due to an increase in frictional resistance and mold scuffing due to seizure. The present invention solves such conventional problems, and a hydraulic press,
An object of the present invention is to provide a surface-treated steel sheet excellent in deep drawability and die galling resistance for stably forming a deep drawn part by a tandem type mechanical press and a transfer press.

[0006]

[Means for Solving the Problems]

 (1) Providing multiple recesses on both sides or one side of the steel plate surface
And the cross-sectional area when the maximum passing length of the recess is d
S, recess depth h, steel plate thickness t, steel plate surface 1 mm ²This
When the number of concave portions is n, the concave depth h is equal to the steel plate thickness t.
0.5-10%, steel plate surface 1 mm²Per recess volume
V representing the total V by V = S × h × n is 0.8 × 10⁶μ
m³Satisfying the above, steel plate surface 1mm²Total disconnection of recesses per hit
Area A is expressed by A = S × n, A is 0.2 mm²Above
In addition, the center distance P between the recesses adjacent to each other in the rolling direction₁Is 1.0
d or more, the center distance P between rows in the rolling direction₂Is 1.0d or more
And the center distance P between the recesses₁And center distance P between rows₂Between
On the surface of the cold-rolled steel sheet in which the depressions are arranged in a zigzag pattern at the positions,
Zn-Ni alloy plating layer on one layer, chromate on the second layer
Deep drawing featuring an organic film on the film and the third layer
It is a surface-treated steel sheet with excellent corrosion resistance, mold galling resistance and corrosion resistance.
It

[0007]

The details of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a vertical cross section of one surface of a surface-treated steel sheet according to the present invention, and FIG. 2 schematically shows a plane surface of the steel sheet for the arrangement of the recesses 1 in FIG. First, the research results up to the present invention will be described. When a steel sheet is deep-drawn by pressing, a large surface pressure acts between the press die and the steel sheet, and the surface pressure crushes the surface roughness of the steel sheet, and a lubricant intervenes. It is known that the boundary lubrication state between the press die and the steel sheet increases, and the frictional resistance increases, and if that state increases, the deep drawability decreases and die galling due to seizure occurs, resulting in poor forming. . In addition, during forming, the temperature of the steel plate and the temperature of the press die also rise due to the heat generated during processing, and the frictional resistance increases due to the deterioration of the performance of the lubricant, which causes a decrease in deep drawability and seizure. This will cause galling, resulting in defective molding. The present inventors consider that an increase in frictional resistance is a fundamental problem of a decrease in deep drawability and the occurrence of galling, and as a measure for preventing the increase in frictional resistance, it can be solved if a sufficient amount of lubricant can be secured. Therefore, the following experimental study was conducted. As the test material, a cold-rolled steel sheet of ultra low carbon titanium-added steel was used. This cold-rolled steel sheet was rolled by a currently used skin pass roll having various dull patterns by electric discharge dull and laser dull processing. Details of these cold rolled steel sheets are shown in Table 1.

[0008]

[Table 1]

The effects of the present invention were examined by applying relative slip between the surface-treated steel sheet of the present invention using the cold-rolled steel sheet shown in Table 1 and the tool and determining the friction coefficient generated at that time. as a result,
Fig. 3 shows the condition of the steel plate surface before and after the relative slip is applied to Fig. 1.
The obtained coefficient of friction is shown. It was found that the surface-treated steel sheet of the present invention has a small coefficient of friction and has a great effect on the increase of the coefficient of friction. From the results of this experimental study, the present inventors further researched, and as a result, found that it was important to secure an appropriate amount of lubricant on the steel plate surface, and by regulating the profile of the steel plate surface as follows. Found that it is possible to provide a surface-treated steel sheet having more excellent deep drawability and die galling resistance.

Next, the reason for limiting the profile of the steel sheet surface in the present invention will be described. First, the reason why the depth of the recess is set to 0.5% or more of the steel plate thickness is that if the depth is less than that, the recess cannot be secured because the recess is crushed by the surface pressure during forming, and the friction resistance increases, The reason why the content is set to 10% or less is that if it exceeds this, there is a risk that the concave portion may serve as a starting point and cause breakage during molding. Next, the reason why the volume of the concave portions per 1 mm ² of the steel plate surface is 0.8 × 10 ⁶ μm ³ or more is that the lubricant is not secured so much and the effect on deep drawability and die galling is small. Further, the total cross-sectional area of the recesses per 1 mm ^{2 of the} steel plate surface is set to 0.2 mm ² or more. Below that, the contact area between the die and the steel plate surface is wide, and the boundary lubrication region is large, so that the friction resistance increases. Therefore, the effect on the deep drawability and the galling is small.

Next, the center distance (P ₁ ) between the concave portions adjacent to each other in the rolling direction is set to 1.0 d or more. When the distance is smaller than that, protrusions are formed due to the overlapping of the concave portions, and the protrusion portions are removed during press forming, so that iron powder This is because there is more generation and the mold gallability is impaired, and the center distance (P ₂ ) between the rolling direction rows is 1.0d.
The reason for the above is that if it is less than that, protrusions are generated due to the overlapping of the recesses, the protrusions are removed during press molding, iron powder is often generated, and mold gallability is impaired. The type of material that can be molded by the present invention may be either a soft steel plate by cold rolling and a high strength steel plate currently specified in JIS, and the plate thickness is 0 when considering automobiles, furniture and home appliances. 0.5-2.0 mm is preferable. Further, in the arrangement of the concave portions shown in FIG. 2, the concave portion group between P ₁ and P ₂ is not necessarily P.
_It is not necessary that the ₁ and P ₂ are bisected, and it is preferable that the recesses do not overlap each other and are arranged between the P ₁ and P ₂ .

In the present invention, a cold-rolled steel sheet having the steel components shown in Table 2 is used as a base material, and a Zn-Ni alloy plating layer, a chromate film, and an organic film are sequentially formed on the surface thereof.
Zn-Ni alloy plating is Zn containing Ni as a main component.
Alloy plating, specifically Zn-Ni, Zn-Ni-Co, Zn-Ni-Fe, Zn-Ni-C
r, Zn-Ni-Fe- Cr such as one containing a metal other than Ni, further _{SiO 2, TiO 2, AlO 2} , Si
It refers to one containing at least one kind of fine particles such as C, SiN, and BaCrO ₄ .

[0013]

[Table 2]

The Ni content is preferably 5 to 20%, and 5%
If it is less than 20%, the corrosion resistance is insufficient, and if it exceeds 20%, the formability is lowered, which is not preferable. If it contains a metal or fine particles other than Ni, it is less than 5% in total, and 2 in total with Ni.
0% or less is preferable. The amount of the Zn—Ni alloy plating layer deposited is not particularly limited, but from the viewpoint of corrosion resistance and formability, it is preferably 10 to 50 g / m ² .
The chromate film adheres the lower Zn—Ni alloy plating layer to the upper organic film and contributes to corrosion resistance. Chromate coating amount is 10 to 1 as total Cr amount
50 mg / m ² is preferable, and if it is less than 10 mg / m ² , the adhesiveness of the organic film is insufficient, and if it exceeds 150 mg / m ² , moldability is deteriorated, which is not preferable. As the chromate treatment liquid, Cr ⁶⁺ and Cr ³⁺ are the main components, and
Inorganic colloids such as O ₂ and TiO ₂ ; acids such as phosphoric acid and molybdic acid and salts thereof; fluorides; water-soluble or emulsion type organic resins; anions such as sulfate ions and halogen ions; Co and Zn Those containing metal ions can be applied.

The organic film acts as a barrier film against corrosion factors such as oxygen, water and chlorine, and provides high corrosion resistance. The thickness of the organic film is preferably 0.3 to 2 μ, and is 0.3
When it is less than μ, corrosion resistance is insufficient, and when it exceeds 2 μ, moldability is deteriorated, which is not preferable. The organic coating may be either a water-soluble resin or a solvent-type resin, but an organic coating containing an epoxy resin and silica as main components is preferable in terms of corrosion resistance and moldability. The method for forming these surface-treated layers is not particularly limited, but the Zn-Ni alloy plating layer is electroplated, the chromate film is electrolytically treated or applied, and the organic film is a roll coater method continuously and at high speed. It is optimal because it allows stable film formation.

[0016]

EXAMPLES Examples of the present invention will be described below together with comparative examples. The test material was an ultra-low carbon titanium-added steel, which was subjected to normal hot rolling-cold rolling-continuous annealing, and was then skin-pass rolled (0.8% reduction) to a plate thickness of 0.8 mm. . In the skin pass rolling, in order to change the profile of the steel sheet surface variously, a skin pass roll having a dull basis weight with a different profile by laser dull processing was used. The surface roughness Ra of the obtained cold rolled steel sheet is JIS
The distance between the recesses, the center distance between the recesses, and the center distance between rows are measured from the optical micrograph of the steel plate surface, and the depth of the recesses is three-dimensional surface roughness. It was determined by a meter. The deep drawability was evaluated by performing 100 high-speed continuous moldings with a punch diameter of 80 mm and a blank diameter of 168 mm, and evaluating the number of moldings until fracture, and the mold galling resistance was 30 when molded. Visually check that there is no problem in quality ○ (good)
The problematic ones were evaluated by x (bad). The results are shown in Table 3.

Examples of cold-rolled steel sheets of the present invention (sample materials 1 to
All of 8) have excellent deep drawability and mold galling resistance as compared with Comparative Examples (samples 9 to 16). Since the test materials 9 and 13 of the comparative example have a small recess depth, the lubricant is less secured due to the crushing during molding, and the deep drawability and die galling cannot be satisfied. Since the sample materials 10 and 14 of the comparative example have a small center distance between the concave portions, the protrusion due to the overlap can be removed, and thus the mold galling is not satisfied. Comparative sample material 1
In Nos. 1 and 15, since the total cross-sectional area of the recesses is small and the volume of the recesses is small, the frictional resistance increases due to the increase in the contact area, and the deep drawability and die galling are not satisfied. The test materials 12 and 16 of the comparative example have a large depth of the recesses, so that breakage occurs, and the galling property and the deep drawability are not satisfied.

[0018]

[Table 3]

[0019]

EFFECTS OF THE INVENTION According to the present invention, it is possible to easily secure molding for a deep-drawing part by a hydraulic press, a mechanical press, and a transfer press for automobiles, furniture, and home electric appliances parts, and to grab the die. It is possible to obtain a good product without causing any noise, and it will be extremely effective for a transfer press, which will become the trend in the future. Therefore, it can be widely used for automobiles, furniture, and home electric appliances, and has great industrial practical value. It is a thing.

[Brief description of drawings]

FIG. 1 is a longitudinal section of a surface-treated steel sheet according to the present invention,

2 is an example of an array of recesses in FIG.

FIG. 3 is a relationship between a laser dull processing condition and a friction coefficient which are the basis of the present invention.

[Explanation of symbols]

1 recessed portion of surface-treated steel sheet 2 cold-rolled steel sheet 3 surface-treated portion t thickness of surface-treated steel sheet h depth of recessed portion of surface-treated steel sheet d maximum penetration length of recessed portion of surface-treated steel sheet S of recessed portion of surface-treated steel sheet Cross-sectional area P ₁ Center distance between recesses adjacent to the rolling direction of the surface-treated steel sheet P ₂ Center distance between rows in the rolling direction of the surface-treated steel sheet

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C25D 5/26 J

Claims (1)

[Claims] 1. A plurality of recesses are provided on both sides or one side of a steel plate surface, and the cross-sectional area is S, the recess depth is h, the steel plate thickness is t, when the maximum transfer length of the recesses is d. Steel plate surface 1m
When the number of recesses per m ² is n, the recess depth h is 0.5 to 10% of the steel plate thickness t, and the total recess volume V per 1 mm ^{2 of} the steel plate surface is represented by V = S × h × n. V is 0.8 × 1
0 ⁶ μm ³ or more, the total cross-sectional area A of the recesses per 1 mm ^{2 of} the steel plate surface is represented by A = S × n, A satisfies 0.2 mm ² or more, and the center distance P between the recesses adjacent to each other in the rolling direction is P. ₁ is 1.0d or more, and the center distance P ₂ between the rolling direction rows is 1.0.
d or more, and the center distance between recesses P ₁ and the center distance between rows P ₂
It is characterized in that a Zn-Ni alloy plating layer is provided as the first layer, a chromate film is provided as the second layer, and an organic film is provided as the third layer on the surface of the cold-rolled steel sheet in which the recesses are arranged in a zigzag pattern at positions between A surface-treated steel sheet with excellent deep drawability, mold galling resistance, and corrosion resistance.