JP2010172944A - Shearing method of coated steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shearing method for suppressing production of enamel hair even when a steel sheet to be sheared has a relatively thick coating film when the coated steel sheet is subjected to the shearing. <P>SOLUTION: When the coated steel sheet 3 is subjected to the shearing by pressing a punch 2 in the coated steel sheet in a state that the coated steel sheet 3 loaded on a die 1 is held by a plate holder, the punch 2 having the corner R at the tip end of a punching blade is used. The corner R of the punch is preferably &ge;0.05 mm and &le;30% of the thickness t of the coated steel sheet to be sheared. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for shearing a coated steel sheet in which the generation of enamel hair is suppressed.

In recent years, products made of coated steel sheets have been widely used as home appliances and automobile parts. In particular, a coated stainless steel plate having a stainless steel plate as a base plate and a clear coating on the surface thereof is frequently used in home appliances aimed at high design.
In addition, from the viewpoint of omitting the process and reducing the cost, a pre-painted steel sheet is used after being pressed into a desired product shape.
In the process of processing a coated steel sheet into home appliances, automobile parts, etc., shear processing such as punching or cutting by a press machine is often performed. And in the case of a shear process, an enamel hair (coating peeling of an end surface) tends to generate | occur | produce on a shear end surface.

When enamel hair is generated on the shear end face, the appearance is deteriorated and the quality of the product is deteriorated, and when it occurs in the process of molding home appliances and automobile parts, it causes a dent and lowers the yield. Is also connected.
Therefore, when the coated steel plate is sheared, the coating on the shear surface is cut in advance, or the shear clearance is extremely reduced to reduce sagging, thereby preventing the occurrence of enamel hair. This is because when the original plate of the coated steel plate is a surface-treated steel plate, if the sag is large, the elongation of the plating layer between the original plate and the coating film is small, so that the portion is easily broken and enamel hair is easily generated.

Specifically, Patent Document 1 proposes that after cutting the film thickness of the coating film in the sheared portion in advance, the punch and die clearance is punched at 5% or more and 10% or less of the plate thickness.
Further, when the original plate is a stainless steel plate, there is no small stretch layer such as a plating layer between the coating film and the original plate, and it is directly coated on the original plate. Therefore, since the size of the adhesion between the original plate and the coating film is directly related to the generation of enamel hair, to prevent the generation of enamel hair, increase the adhesion between the coating film and the original plate, or reduce the thickness of the coating film as much as possible. It is necessary to make it thinner.

Japanese Patent Laid-Open No. 9-3000295

In the method proposed in Patent Document 1, a film thickness is cut in advance in the coating film on the sheared portion by punching. For this reason, the shearing process itself is complicated and the productivity is lowered.
In addition, in the case of a coated stainless steel sheet in which a clear coating film is formed on a stainless steel sheet, a thick coating film is required when trying to express a desired high design. As the thickness increases, enamel hair is more likely to occur. Generally, when the coating film is 5 μm or more, it becomes difficult to completely prevent enamel hair. And when enamel hair generate | occur | produces, the operation | work remove | eliminated after a process is needed, workability | operativity becomes very bad.

  The present invention has been devised to solve such problems. When shearing is applied to a coated steel sheet, enamel hair is generated even if the processed sheet is a coated steel sheet having a relatively thick coating film. An object of the present invention is to provide a shearing method that suppresses the above.

In order to achieve the purpose of the shearing method of the coated steel sheet of the present invention, in the state where the coated steel sheet placed on the die is pressed with a sheet presser, when the punch is pushed into the coated steel sheet and shearing is performed, A punch provided with a corner R at the tip of a shearing cutter is used as the punch.
The corner R of the punch is preferably 0.05 mm or more and 30% or less of the thickness t of the coated steel sheet to be processed.

  In the shearing method of the coated steel sheet according to the present invention, the generation of enamel hair can be suppressed by applying a corner R to the cutting edge of the punch. For this reason, it is not necessary to perform the removal work of enamel hair after processing as before, and workability is improved. In addition, since the dent is eliminated, the product yield is greatly improved.

Diagram explaining the generation mechanism of enamel hair during shearing Diagram explaining the mechanism to prevent enamel hair generation during shearing

The inventors of the present invention have intensively studied the cause of enamel hair that occurs when shearing is applied to a coated steel sheet, particularly a coated stainless steel sheet that has been subjected to clear coating, and countermeasures thereof.
First, looking at the cause of enamel hair generation, the generation of enamel hair at the shear end face is presumed to be a phenomenon in which the coating film peels off at the interface with the original plate.
This phenomenon will be described with reference to the drawings.

  As shown in FIG. 1, when the coated steel plate 3 placed on the die 1 is subjected to a shearing process using the punch 2 (a), the cutting edge of the punch 2 first bites into the coating film 5 and the coating film is sheared. (B). Thereafter, the cutting edge of the punch 2 bites into the original plate 4 which is the material, the original plate is sheared (c), and separated into a punching residue and a punching die (d). When the cutting residue is separated and shearing is finished, the punch is pulled upward and the cutting edge is detached from the material (e), the coating film end face and the cutting edge side face slide with high surface pressure, and the coating film 5 Force acts in the direction of peeling from the original plate 4. And it is estimated that the coating-film edge peeled off when the blade edge | part separated from the material will detach | leave from a main-body part, and will become enamel hair.

The thicker the coating film that contacts the side surface of the punch blade edge, the stronger the influence of the action of peeling the coating film from the original plate when the cutting edge is detached from the material, and the coating film is thinly stretched and sheared. The lower the effect of sliding from the side of the blade, the less the peeling at the coating film edge occurs, and as a result, the generation of enamel hair becomes difficult.
Therefore, the present invention has been devised so that the edge of the coating film is not peeled off or detached from the main body during shearing.
That is, as a punch for shearing, using a cutting edge with a slight corner R, cutting the coating film rather than shearing the coating film with poor sharpness as a cutting tool, It was decided to suppress the generation of enamel hair.

When a shearing process is performed using a punch having a slight corner radius R on the cutting edge, as shown in FIG. 2, the cutting edge of the punch 2 first bites into the coating film 5 (b). The cutting edge portion having R bites the coating film 5 so as to extend thinly along the corner R surface.
After that, even when the punch blade edge bites into the material (c), since the corner R is attached to the punch blade edge, the shearing of the material starts with a delay (d).

And, while further extending the thinly stretched coating film end, in a form to press the thinly stretched coating film end against the sagging surface of the material, the punch blade edge bites into the steel plate that is the material, The extracted residue is separated and the shearing process ends (e). When the punch is pulled upward after the shearing process is finished (f), the coating film end face and the blade tip end slide at a high surface pressure. The sliding form at this stage is the above-described normal punch. It is different from the case of using.
When the punch is pulled upward, the coating film edge that is thinly stretched and pressed against the sag surface of the work material becomes difficult to peel off due to less sliding effect with the blade tip, resulting in enamel It is presumed that the generation of hair is suppressed.

In addition, although the generation | occurrence | production condition of enamel hair changes also with the presence or absence of use of a lubricating film, in order to suppress the generation | occurrence | production reliably, it is preferable that the corner R attached | subjected to a punch blade edge shall be 0.05 mm or more. If the corner R is less than 0.05 mm, the enamel hair generation suppressing effect is hardly seen.
On the other hand, when R is so large that it exceeds 30% of the thickness t of the coated steel sheet to be processed, the sagging becomes too large, and the shape of the cut surface after the shearing process is significantly deteriorated.
Therefore, it is preferable that the corner R attached to the punch blade edge is 0.05 mm or more and 30% or less of the thickness t of the coated steel plate to be processed.

Next, we introduce an example of applying shear processing to a coated stainless steel sheet with clear coating. The raw material is a SUS430 cold-rolled annealed plate having a thickness of 0.5 mm having mechanical properties shown in Table 1, and the surface thereof is subjected to a polymer acrylic clear coating with a thickness of 6 μm.
The conditions shown in Table 2 were adopted as the shearing conditions. No processing oil or protective film was used.
And the generation | occurrence | production situation of the enamel hair after a shearing process and the shape of the edge part of processed goods were observed.
The results are shown in Table 3. In the table, “occurrence” and “none” in the EH column indicate that enamel hair has occurred and has not occurred, and “good” and “sag” in the shape column indicate that the end shape is good. This indicates that there was a sag.

From the results shown in Table 3, it can be seen that the generation of enamel hair can be surely prevented when shearing is performed using a punch with a corner R attached to the tip of the blade edge. However, if the corner R is too large, sagging occurs and the molding accuracy of the product is reduced.
Therefore, it is preferable that the corner R attached to the tip of the punch edge is set to an appropriate size.

Claims (2)

  In the state where a coated steel plate placed on a die is pressed by a plate presser and a shearing process is performed by pressing a punch into the coated steel plate, a punched blade tip imparted with a corner R is used as the punch. A method for shearing coated steel sheets.   The method for shearing a coated steel sheet according to claim 1, wherein a punch having a radius R of 0.05 mm or more and 30% or less of the thickness t of the coated steel sheet is used as the corner R of the punch.

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