JPH05237506A - Steel plate with excellent workability - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a mild steel plate and a high-tensile steel plate having excellent press workability. According to the gist of the present invention, a flat portion is provided on the bottom surface of the concave portion on the surface of the steel sheet in order to improve the oil collecting performance on the surface of the steel sheet and to further secure the oil collecting effect by having a uniform concave portion on the surface of the steel sheet. However, when the recess is provided, the diameter of the recess is 2
The present invention provides a mild steel plate and a high-tensile steel plate having a recess pitch of 0 to 600 μm, a recess pitch of 10 to 1000 μm, and a recess depth of 1 to 20 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet having good workability and paint clarity in mild steel sheets and high-tensile steel sheets with little elongation when press-formed on outer panels of automobiles and home electric appliances. Is.

[0002]

In recent years, steel sheets for automobiles have been required to be light in weight due to improvement in fuel consumption and environmental problems, and various high-tensile steel sheets have been developed for thinning the steel sheets. In addition, increasing the tensile strength of steel sheets has been drawing attention from the viewpoint of safety of automobiles, and it is expected that the tensile strength will further increase in the future. As the tensile strength of steel sheets for automobiles decreases, the workability of steel sheets (material plastic elongation) decreases, so in the development of high-strength steel sheets, how to secure high tension and material elongation is an issue, and many studies have been conducted. There is.

On the other hand, in order to avoid partial restraint in the press working, a lubricant used in the press working has been developed. This is to increase the viscosity of the lubricating oil in order to improve the oil film forming ability during press working, and to prevent partial seizure by using an extreme pressure additive. In securing material elongation aiming at improvement of press workability of high-tensile steel sheet, reduction of material elongation cannot be avoided due to higher tensile strength, and improvement of workability cannot be expected. Therefore, improving the lubrication ability is considered to be a good way to improve the workability, but if the viscosity of the lubricating oil is increased, the deterioration of the existing mechanical capacity and the cleaning capacity in the subsequent stage becomes a major problem, and Has a limit and cannot be raised so much. In addition, since the effect of the extreme pressure additive is basically a reaction type, the addition of a large amount of the extreme pressure additive affects the cleaning property and the coating property. Under such circumstances, the present invention provides a mild steel plate and a high-tensile steel plate with significantly improved press workability.

[0004]

DISCLOSURE OF THE INVENTION The gist of the present invention is to improve the oil pooling performance on the surface of a steel plate by having a uniform recess on the surface of the steel plate and to further secure the effect of pooling the surface of the steel plate. The present invention provides a mild steel plate and a high-tensile steel plate having a flat portion on the bottom surface. When forming the recesses, the diameter of the recesses is 20 to 600 μm, and the recess pitch is 10 to 10
The range of 00 μm and the depth of the recess is preferably 1 to 20 μm.
That is, the present invention, in order to obtain a good press working method of mild steel plate and high-strength steel plate, conventionally, the development of materials and lubricants have been made, but by further imparting an oil sump effect to the steel plate It is intended to improve workability.

In general, in order to make the surface of a steel sheet uneven, rolling the annealed steel sheet with a temper rolling roll having unevenness is the cheapest and most stable production. There is a high-density laser processing method for processing the temper rolling roll. The surface schematic diagram of the steel plate manufactured by this method is shown in FIG. According to this method, the ring-shaped oil reservoir 1
However, since the center portion 2 of the ring rises, the first contact occurs at the center portion 2 of the ring where the press die and the steel plate are raised during the press working, so that the oil sump portion 1 cannot be effectively opened. Further, there is a limit in the oil sump area and the oil sump volume obtained by this roll processing method, so that an optimum oil sump groove cannot be obtained. Therefore, to ensure the oil sump effect, a tempered rolling roll is processed by a microlithography method to form a uniform recess without a raised portion, and then tempered rolling is used to form uniform unevenness on the surface of the steel sheet to improve press workability. Tested. FIG. 2 is a schematic diagram of a steel plate surface obtained by this method. In this case, the concave portion 3 has a sealed shape.

FIG. 3 shows the relationship between the mark shape and mark pitch obtained by this method and the oil pool area ratio on the steel plate. The shape range in FIG. 3, for example in the case of ○ shape when the arc concave as shown in FIG. 4 is present independently when independent: maximum area ratio of the {independent conditions 2r <P} is, S _O (hatched Part) = [πr ² / P ² ] × 100 (%) S _max is when 2r = P. S _max = [πr ² / P ² ] × 100 = 78% (theoretical value) Further, as a typical manufacturable range in the case of the O shape, as shown in FIG. 4B, the circle size D = 200 μm When the distance is 30 μm, S = [πr ² / P ² ] × 100 = 60%.

That is, the range of the O shape indicates that the oil storage area can be manufactured up to 60%. Similarly, as for the □ shape, as shown in FIG. 5, when the □ shaped recesses exist independently, in the independent case {independence condition:
The maximum area ratio of d _O <P} is S _O (hatched portion) = [d _O ² / P ² ] × 100 (%) S _max is when d _O = P. S _max = [d _O ² / P ² ] × 100 = 100% (theoretical value)

In the case of the present invention, when the recesses are provided, the diameter of the recesses is 20 to 600 μm, the recess pitch is 10 to 1000 μm,
The recess depth is preferably in the range of 1 to 20 μm, and as shown by the findings of the inventors of FIG. 3, according to this method, the oil sump area can be increased to 90% by selecting the mark. , 30% by high density laser method
It can only be done to a certain degree. Further, the shape of the recess is not limited to the O and □ shapes, and the effect is the same even if it is Δ or polygonal. Further, when forming a fine pattern on the rolling roll, it is preferable to regularly arrange the recess pattern arrangement at each apex of the triangle, and the shape of the recess is not specified whether it is a quadrangle / pentagon or a polygon. Alternatively, it is preferable to dispose two kinds of large and small concave portions at each apex of a triangle, and the concave portion arrangement may be arranged in a square, pentagon or polygon. Further, the sizes of the patterns are not limited to two types as long as they are large and small.

FIG. 6 shows a press workability test apparatus. The steel plate 4 was pressed against the upper and lower dies 5 and 6 with a constant load, and the steel plate 4 was pulled upward to evaluate the press workability of the steel plate 4 by the breaking load of the steel plate 4. The results of press workability of the steel sheet processed by this method are shown in FIG. The press workability increases as the oil pool area ratio on the steel plate surface increases, and good workability can be obtained at 30% or more. The steel sheets targeted by the present invention are cold-rolled steel sheets, surface-treated mild steel sheets and high-tensile steel sheets, and high-tensile steel sheets are cold-rolled steel sheets having high tension of 35 kgf / mm ² or more and surface-treated steel sheets. Say a steel plate made.

In order to obtain the steel sheet of the present invention, it is advantageous to obtain a fine pattern on a rolling roll by using, for example, a microlithography method, and to roll the steel sheet using the rolling roll. Such a rolling roll is usually used as a temper rolling roll after annealing, and when hot-dip coating is performed after annealing like a hot-dip galvanized steel sheet, it is used as a temper rolling roll after that. If necessary, temper rolling using a discharge dull roll, a shot dull roll, or a bright roll is performed before or after rolling with a microlithography roll. That is,
It is also possible to carry out a temper rolling twice. Further, the method of the present invention improves the flaw resistance by using a microlithography roll as the final stand roll of the cold rolling mill because it improves the flaw resistance, and improves the flaw resistance at the time of sheet passing in the process after annealing or plating. Therefore, high quality products can be manufactured. In this case, for annealing or temper rolling after annealing / plating, any of a microlithography roll, a discharge dull roll, a shot dull roll, and a bright roll can be adopted.
Rolling can also be applied.

The most typical applications requiring workability are interior and exterior plates for automobiles and interior and exterior plates for home appliances. Conventionally,
Cold-rolled steel sheets have been used for such applications, but recently, against the backdrop of rust prevention strengthening trends in all industries, hot-dip galvanized steel sheets in consideration of workability, alloyed hot-dip galvanized steel sheets,
Fe-Zn electroalloy-plated two-layer alloy hot-dip galvanized steel sheet, electrogalvanized steel sheet, Fe-Zn-based single-layer or two-layer electrogalvanized steel sheet, Zn including those coated with resin -The adoption of Ni-based galvanized steel sheets and the like is being expanded. The present invention imparts particularly excellent workability to these surface-treated steel sheets in addition to the cold-rolled steel sheet.

In the alloyed hot-dip galvanized steel sheet and the two-layer alloy hot-dip galvanized steel sheet subjected to Fe-Zn electroalloy plating, in the alloying process after hot-dip galvanization, F
e-Zn Binary alloy crystals generate irregular irregularities on the surface, and irregularities are more effective for workability than the cold-rolled steel sheet, but the strength of the plating layer is lower than that of the material, so it is convex during processing. There was a problem that the parts were broken and the workability was deteriorated.
In the present invention, the surface unevenness profile control far exceeding the prior art is possible by the method described later, and the performance improving effect in such quality is particularly remarkable.

In the case of electrogalvanized steel sheets in general and hot-dip galvanized steel sheets not subjected to the alloying treatment, the surface roughness due to the thermal diffusion reaction does not occur significantly, but the strength of the plated layer is higher than that of the cold-rolled steel sheet. Since it is low, the workability deteriorates as the plating thickness increases. In order to eliminate these influences and improve workability, the present invention is overwhelmingly superior to the conventional method. It goes without saying that the present invention is effective not only for cold-rolled steel sheets and galvanized steel sheets but also for tin-plated steel sheets, can steel sheets centered on Cr-plated steel sheets, aluminized steel sheets, and stainless steel sheets.

[0014]

【Example】

Example 1 φ550 mm × L18 by microlithography method
On the surface of the temper rolling roll 7 of 00 mm, as shown in FIG.
The annealed high-tensile cold-rolled steel sheet was rolled using a roll having a pattern having a distribution of protrusions 8 and recesses 9 having a protrusion height of 300 μm and a height of 5 μm, and press workability was evaluated by an actual press. The high-strength steel sheet has an oil pool area ratio of 65% on the surface. As the high-tensile steel plate, a 60K class high-tensile steel in which Si was added to a low C type was used. Table 1 shows the number of press cracks in an actual press, but the high-strength steel sheet according to the present invention gave good results without one press crack. Although Table 2 shows the occurrence of press flaws, similar good results were obtained for press flaws.

[0015]

[Table 1]

[0016]

[Table 2]

Example 2 φ550 mm × L18 by microlithography method
On the surface of the temper rolling roll 7 of 00 mm, as shown in FIG.
The cold-rolled mild steel sheet after annealing was rolled using a roll having a pattern having a projection 8 and a recess 9 having a projection height of 300 μm and a height of 5 μm, and the press workability was evaluated by an actual press.
The surface area of the mild steel plate has an oil pool area ratio of 65%. As the mild steel sheet, a low C type 30K grade material was used. Table 3 shows the number of press cracks in an actual press, but with the mild steel sheet according to the present invention, a good result was obtained without one press crack. Although Table 2 shows the occurrence of press flaws, similar good results were obtained for press flaws.

[0018]

[Table 3]

[0019]

[Table 4]

Example 3 φ550 mm × L18 by microlithography method
On the surface of the temper rolling roll 7 of 00 mm, as shown in FIG.
A pattern having a distribution of protrusions 8 and recesses 9 having a protrusion height of 5 μm of 300 μm was formed. Using the work roll, the cold-rolled steel sheet after annealing having a thickness of 0.8 mm and the alloyed hot-rolled steel sheet were temper-rolled at a rolling reduction of 0.8%, and recessed on the surface of the steel sheet 10 as shown in FIG. Eleven profiles were formed. The basis weight of the alloyed hot-dip galvanized steel sheet is 60 g / m ² per side, and in the case of the two-layer type alloyed hot-dip galvanized steel sheet subjected to Fe-Zn electroalloy plating, the basis weight of the hot-dip coating layer is 60 g / side. m ² and the electroplated layer were 4 g / m ² (Fe content 80% by weight). The adhesion of the plating layer was all good. The obtained steel sheet was evaluated for workability in the press workability evaluation test shown in FIG. 6 with the die pressing load kept constant at 35 kg. The results are shown in Table 5.

According to Table 5, the test N according to the present invention is used.
o. 2 to 3 and 7 to 11, 16 to 17 and 20 to 21 are those of the conventional system test Nos. According to the methods of Comparative Examples 1 and 4 to 6, 14 to 15 and JP-A-63-132701. Compared with Nos. 12 to 13, 18 to 19, and 22 to 23, markedly good results are shown in the evaluation of press workability as a characteristic value.

[0022]

[Table 5]

[0023]

EFFECTS OF THE INVENTION By using the present invention, the surface of mild steel plate and high-strength steel plate, which were conventionally inferior in press workability, can be coated with 30
%, The mild steel plate and the high-tensile steel plate having unprecedented good press workability can be obtained by providing an oil sump having a uniform concave portion of not less than%.

[Brief description of drawings]

FIG. 1 is a schematic diagram of the surface of a steel plate manufactured by a high-density laser,

FIG. 2 is a schematic diagram of a surface of a recessed steel plate obtained by a microlithography method,

FIG. 3 is a relationship between oil sump area ratios obtained by the microlithography method,

FIG. 4A is a schematic view of a steel plate surface when the maximum area of an arcuate recess is obtained;

FIG. 5 is a schematic diagram of a □ -shaped recess,

FIG. 6 is a press workability test device,

FIG. 7 (a) is a view showing a result of press workability of mild steel plate;
(B) A diagram showing results of press workability of high-tensile steel plate,

FIG. 8A is a schematic view of a roll processed by a microlithography method, and FIG. 8B is an enlarged view of a convex portion of the same.

FIG. 9 is a schematic view of the surface of a steel sheet manufactured by rolling.

[Explanation of symbols]

 1 Oil Puddle 2 Ring Center 3 Recess 4 Steel Plate 5 Upper Die 6 Lower Die 7 Roll 8 Roll Convex 9 Roll Recess 10 Steel Plate Surface 11 Steel Recess

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Kawano 5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Co., Ltd. Nagoya Steel Works

Claims (3)

[Claims] 1. A steel sheet having excellent workability, characterized in that it has uniform recesses on the surface of the steel sheet. 2. The steel sheet having excellent workability according to claim 1, wherein the steel sheet has a flat portion on the bottom surface of the recess. 3. The steel sheet having excellent workability according to claim 1, which has an oil reservoir area of 30% or more on the surface of the steel sheet.