JPH0691305A - Zinc plated steel sheet excellent in deep-drawability, resistance to die galling and corrosion resistance - Google Patents

Abstract

PURPOSE:To provide a zinc plated steel sheet excellent in deep-drawability, resistance to die galling and corrosion resistance for easily and stably manufacturing it at the time of manufacturing deep-drawn parts which are used for automobiles, furnitures, house appliances, etc., by press forming. CONSTITUTION:The zinc plated steel sheet excellent in deep-drawability, resistance to die galling and corrosion resistance is easily and stably manufactured by providing plural concave parts 1 on the surface of steel sheet in zigzag, taking the depth (h) of the concave part as 0.3 to 10% of thickness (t), the total cross-sectional area of the concave parts per 1mm<2> of the surface of steel sheet as >=0.3mm<2>, the total volume of the concave parts as >=0.8X10<6>mum<3> the distance between the concave parts as >=1.0 of the max. diameter of the concave part and executing the zinc plating on the surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc-based plated 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. is there.

[0002]

2. Description of the Related Art Conventionally, in forming deep drawing parts such as oil pans 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, and the temperature of the press die also rises 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-drawn parts as well, the influence of a rise in the die temperature becomes extremely large, and the molding due to the deterioration of deep-drawability and the occurrence of mold scuffing. The problem of poor sex began 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 increasing the number of drawing steps to reduce deformation heat generation, but the increase in the number of molds increases the manufacturing cost etc. However, the actual situation is that the measures are not always satisfactory.

Further, 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 a Japanese Patent No. 8602 (painting steel plate and manufacturing method thereof). Its content is excellent in coating image clarity by regularly controlling the roughness, and does not mention the zinc-based plated steel sheet excellent in deep drawability and die galling resistance of the present invention and suggests nothing. Does not give.

[0004]

As described above, when forming a deep-drawn part in the conventional galvanized steel sheet, the temperature of the part and the die 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 the above-mentioned conventional problems and stably forms a deep-drawn part by a hydraulic press, a tandem mechanical press, and a transfer press, and has excellent deep drawability, mold galling resistance, and corrosion resistance. The purpose is to provide a plated steel sheet.

[0005]

[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 ² This
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 mm² Per recess volume
V representing the total V by V = S × h × n is 0.8 × 10⁶μ
m³ Satisfying the above, steel plate surface 1mm² Total number of recesses per hit
A representing the cross-sectional area A by A = S × n is 0.2 mm² The above
Satisfaction, center distance P between recesses adjacent to each other in the rolling direction₁Is 1.
0d or more, rolling center row-to-row center distance P₂Is 1.0d or less
Above and center distance P between recesses₁And center distance P between rows₂of
Cold rolled steel with zigzag pattern formed by arranging recesses in the space
Providing a plating layer containing 70% or more of zinc on the surface of the plate
Deep drawability, mold galling resistance and corrosion resistance
Excellent galvanized steel sheet.

[0006]

The details of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a vertical cross section of one side of a galvanized steel sheet according to the present invention, and FIG. 2 schematically shows the plane of the steel sheet surface 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 the state increases, the deep drawability decreases and seizing causes die galling, resulting in defective 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 the increase in frictional resistance is the fundamental problem of the decrease in deep drawability and the occurrence of mold galling.
As a measure to prevent the increase of the frictional resistance, it was thought that it could be solved if a sufficient amount of lubricant could be secured, and the following experimental study was conducted. As the test material, the cold-rolled steel sheet of ultra low carbon steel shown in Table 1 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. Table 2 shows the details of these cold rolled steel sheets.

[0008]

[Table 1]

[0009]

[Table 2]

The effects of the present invention were examined by providing a relative slip between the galvanized steel sheet of the present invention using the cold-rolled steel sheet of Tables 1 and 2 and the tool, and determining the friction coefficient generated at that time.
As a result, FIG. 1 shows the condition of the steel sheet surface before and after the relative slip, and FIG. 3 shows the obtained friction coefficient. The galvanized steel sheet of the present invention has a small friction coefficient and a large effect on the increase of the friction coefficient. I found out that 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. Have found that a galvanized steel sheet having excellent deep drawability and die galling resistance can be provided.

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 shorter than that, protrusions are generated 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 increased, and the mold gallability is impaired. The type of material that can be formed by the present invention may be either a soft steel plate by cold rolling and a high strength steel plate currently defined in JIS, and the plate thickness when considering automobiles, furniture, and home appliances. 0.5 to 2.0 mm is suitable. Further sequence of the recess shown in FIG. 2, depressions falling between P ₁ and P ₂ are not necessarily in the P ₁ and P ₂ in bisecting position, do not overlap the recess each other, and P ₁ It is preferable to arrange between P and P ₂ .

In the present invention, a cold-rolled steel sheet having the steel components shown in Table 1 is used as a base material, and a zinc plating layer containing 70% (mass ratio) or more of zinc is formed on the surface thereof. Here, the zinc-based plating layer means pure Zn plating, Ni, Fe, C
o, Cr, Al, Mn, Cu, Sn, Pb, Cd, M
Metals such as g; SiO ₂ , TiO ₂ , Al ₂ O ₃ , S
Zinc alloy plating or zinc composite plating containing one or more fine particles of iC, SiN, BaCrO _4, etc. When a component other than zinc is contained, if the zinc content is too low, the sacrificial anticorrosive action of the plating layer decreases and the corrosion resistance is impaired, or the formability decreases due to hardening of the plating layer. is necessary.

The amount of the zinc-based plating layer deposited is not particularly limited, but is preferably 10 to 100 g / m ² from the viewpoint of corrosion resistance and formability. Further, it may be a mode of multi-layer plating in which two or more kinds of plating layers having different component systems are stacked depending on the purpose. The method for forming these zinc-based plating layers is not particularly limited, and any method such as electroplating, hot dipping, chemical plating, vapor-phase plating represented by vapor deposition may be used. However, the electroplating method and the hot dipping method are more preferable methods in that they can continuously and rapidly perform plating on the cold-rolled steel sheet at high speed.

[0015]

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 skin pass rolling, in order to change the profile of the steel sheet surface, various types of plating were performed by electroplating or hot dip coating on skin pass rolls having different dull weights by laser dull processing. The surface roughness Ra of the obtained galvanized steel sheet is JI
Determined by the measurement method specified in S, and the passing length of the recesses, the center distance between the recesses, and the center distance between rows are measured from an optical micrograph of the steel plate surface, and the depth of the recesses is the three-dimensional surface. It was determined by a roughness meter. The evaluation of deep drawability is
High-speed continuous molding was performed with a punch diameter of 80 mm and a blank diameter of 168 mm up to 100 pieces, and the number of pieces formed up to fracture was evaluated, and mold galling resistance was a visual quality problem when the 30 pieces were formed. There is no ○
(Good), those having a problem were evaluated by x (bad). The results are shown in Table 3.

The examples (specimens 1 to 8) of the galvanized steel sheet of the present invention are more excellent in deep drawability and die galling resistance than the comparative examples (specimens 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. In each of the test materials 11 and 15 of the comparative example, since the total cross-sectional area of the recesses is small and the volume of the recesses is small, the frictional resistance is increased due to the increase of 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 recess, so that breakage occurs, and the mold gallability and the deep drawability are not satisfied.

[0017]

[Table 3]

[0018]

According to the present invention, it is possible to easily secure the molding and to prevent the galling of deep drawn parts by hydraulic press, mechanical press and transfer press for automobiles, furniture and home electric appliances. It is possible to obtain a good product with excellent corrosion resistance without generating it, and it will be extremely effective for a transfer press that will become a trend in the future.
It can be widely used for automobiles, furniture, and home electric appliances, and has industrially great practical value.

[Brief description of drawings]

FIG. 1 is a longitudinal section of a zinc-based plated 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 zinc-based plated steel sheet 2 Cold-rolled steel sheet 3 Zinc-based plated steel sheet portion t Thickness of zinc-based plated steel sheet h Depth of recessed portion of zinc-based plated steel sheet d Maximum penetration length of recessed portion of zinc-based plated steel sheet S Cross-sectional area of recesses of zinc-based plated steel sheet P ₁ Center distance between recesses adjacent to each other in the rolling direction of the zinc-based plated steel sheet P ₂ Center distance between rows in the rolling direction of the zinc-based plated steel sheet.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C23C 30/00 B

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 [mu] m ³ satisfy the above total cross-sectional area A of the steel sheet surface 1 mm ² per recess A = S × A is 0.2 mm ² represented by n
Satisfying the above, center distance P ₁ between the recesses adjacent to each other in the rolling direction
Is 1.0 d or more, and the center distance P ₂ between the rolling direction rows is 1.
A plated layer containing 0% or more of zinc and 70% or more of zinc on the surface of a cold-rolled steel sheet having a zigzag pattern in which a group of recesses is arranged at a position between the center distance P ₁ between recesses and the center distance P ₂ between rows. A zinc-based plated steel sheet with excellent deep drawability and galling resistance, which is characterized by being provided.