JP4999156B2 - Punching method for copper-plated steel sheet - Google Patents

Description

  The present invention relates to a punching method for leaving a copper plating layer on an end surface formed by punching when a copper-plated steel sheet is punched.

  Copper-based materials are used for electrical / electronic parts, fastener parts, and the like for the purposes of electrical conductivity, rust prevention, workability, and the like. However, since copper is very expensive, recently, the use of a copper-plated steel sheet in which a copper base is plated with copper for the purpose of cost reduction is increasing. And electrical / electronic parts, fastener parts, and the like made of copper-plated steel sheets are produced by a combination of various processing processes such as drawing, bending, and punching. In particular, punching is frequently used for the purpose of creating bent parts, positioning, trimming process products, and the like.

In the punching process of a steel plate, a cavity shape is formed by inserting a steel plate (blank) M cut into a predetermined size between a die D in which a cavity having a predetermined shape is formed and a punch P, and pressing the punch P into the die D. I have a stamped product.
When a copper-plated steel sheet having the plating layer L is punched with a conventional mold, the corners of the punch and the die cut off the plating layer L as shown in FIG. When a new surface is generated on the processed end face of a punched product, problems such as deterioration of electrical conductivity and rusting are caused.

In order to suppress the deterioration of electrical conductivity and the generation of rust, it is necessary to re-apply copper plating to the processed end face of the punched product, but it is extremely difficult in practice. For this reason, the use of the punched product made of a copper-plated steel sheet is limited to the use that does not require copper plating on the punching end face. Therefore, there is a technology for applying a stamping or the like to the processed edge of the punched product so as to cover the plated layer formed on the surface of the steel sheet up to the punched end surface. This is proposed in Patent Document 1.
Japanese Patent Laid-Open No. 9-13182

However, since the technique proposed in Patent Document 1 also re-processes the punched end, it leads to a significant cost increase and is not practical as with the re-plating.
The present invention has been devised in order to solve such problems, and is capable of simply punching a copper-plated steel sheet capable of leaving a copper-plated layer on the processed end face of a punched product. An object is to provide a processing method.

In order to achieve the object, the copper-plated steel sheet punching method of the present invention has a punch shape of Rp / t ≧ 0.06 and a die shape of Rd / t ≧ 0.06. Use a half-punch die to perform half-punching of negative clearance, and then the punch shape is the same diameter as the punch that has been half-punched, and the concave part that fits the half-pumped convex part on the tip surface And a copper plating remains on the entire surface of the punched end face by punching from the opposite direction with a die having Rp / t ≧ 0.06.

According to the method of the present invention, it is possible to leave a copper plating layer on the punched end face, and therefore, even if a copper plated steel sheet is used as a material, it is easy to manufacture a punched part that has excellent electrical conductivity and can maintain a rust prevention function. Can do.
Therefore, it is possible to use copper-plated steel sheets for parts that could not be applied due to problems such as deterioration of electrical conductivity and rusting, and the material cost can be significantly reduced by replacing copper with copper-plated steel sheets. It becomes possible.

When a normal punching process is performed using a plated steel sheet as a blank, as shown in FIG. 1 (c), the plated layer L is cut at the end face of the punching process, a new surface appears, and the original corrosion resistance of the plated steel sheet deteriorates. In the case of a copper-plated material, the electrical conductivity expected of the plated copper is also lowered.
The reason for the plating layer breakage at the punching end face is that the clearance between the die and the punch is small, so when the blank is pressed against the die wall by the punch and cut, It can be torn off.

Therefore, it is assumed that the clearance between the die and the punch is increased so that the plating layer is plastically flowed in accordance with the plastic deformation of the blank material, and the fracture surface is covered with the plastic layer that is plastically flowed when the blank material is broken. .
However, when a punching process is performed with a mold having a large clearance, a large burr is formed. Moreover, it is difficult to cover the entire burr with a plating layer.

The inventors of the present invention studied a method for punching a plated steel sheet that can suppress the generation of burrs and cover the fracture surface with a plating layer.
As a result, first of all, a steel plate plated with copper with excellent plastic deformability is half-punched using a die with a negative clearance by making the outer diameter or length of the punch larger than the inner diameter or length of the die. After that, it was found that it is effective to employ a means for punching from the opposite surface to form a punched hole.
Details will be described below.

When the blank M is punched using a die having a negative clearance between the punch P ₁ and the die D ₁ as shown in FIG. 2, as shown in FIG. 2 (b), the die D ₁ The blank M is sheared along the wall surface of the die D ₁ and the punch P _{1 at} a stage where the amount of the punch P ₁ pushed in is small. Since the copper plating layer L on the surface of the blank M is richer in ductility than the base steel, it plastically flows along the walls of the die D ₁ and the punch P ₁ . As a result, a sheared surface is formed which has no fracture surface and is covered with the plating layer L. In such a manner, half blanking is performed to the position shown in FIG. 2C, preferably 60 to 95% of the plate thickness. If the half blanking is performed to exceed 95% of the plate thickness, the copper plating layer may be cut. On the other hand, if half blanking that is less than 60% of the plate thickness is performed, it is difficult to perform punching in the next step.

Next, the punch P ₂ is punched in from the opposite side of the half-cut surface. As an aspect thereof, as shown in FIG. 2D, first, the punch P ₁ used in the half-cutting process is replaced with a counter, and the blank holder is replaced with a die D ₂ . Alternatively, the punch P ₁ and the blank holder may function as the counter and the die D ₂ as they are. Then, against the blank holder from the opposite side of the pushed it faces the half die punch, pushed back upwards the half blanking portion added punch force exceeding a counter-force in the punch P _2. At the time of this pushing back, the blank M is sheared along the half-cut stepped portion. The copper plating layer L on the surface of the blank M also plastically flows along the stepped portion. As a result, when the steel sheet of the blank base material is broken, the end face is covered with a plastic-plated copper plating layer.
Note that when pushed back upwardly half blanking portion in the punch P _2, as the punch, the semi-punching punch and the same diameter, recesses, such as half-blanking is convex is fitted to the front end surface is formed Is preferred.

Thus, since the copper plating layer is superior in plastic deformability as compared with the base steel plate, the processed end face can be covered with the copper plating layer at the time of punching.
However, even if the copper plating layer has excellent plastic deformability, it does not mean that desired processing can be performed in any manner. Depending on the shape of the punch or die used, or depending on the amount of pressing of the punch, the plastic deformation of the copper plating layer cannot follow the movement of the punch or die, and the plating layer may be cut.

Therefore, the present inventors investigated the influence of the shape of the punch or die on the copper plating layer breakage. As a result, the details will be given in the embodiment, but when punching a steel sheet having a thickness t, first, the punch shape is Rp / t ≧ 0.06 and the die shape is Rd / t ≧ 0.06. If the punch shape is punched from the opposite direction with a die with a punch shape of Rp / t ≧ 0.06, the copper plating layer is not cut and the processed end face is It was found that a punched product covered with a copper plating layer was obtained.
If the Rp of the punch and the Rd of the die were less than 0.06 times the plate thickness t, the plastic deformation of the copper plating layer could not follow the movement of the punch or the die, and the copper plating layer was cut.

In this way, when half-cutting is performed using a half-clearance die with a negative clearance and then punching is performed in the reverse direction, the copper plating layer is not cut and the processing end face is covered with the copper plating layer. A punched product is obtained.
Since the processed end face is also covered with the copper plating layer, a punched part that can maintain excellent electrical conductivity and excellent rust resistance based on the copper plating layer can be manufactured at low cost.

Example 1:
A copper-plated steel sheet in which copper was electrodeposited with a film thickness of 3 μm was used on a cold-rolled steel sheet having a thickness of 1.6 mm. S-102k manufactured by Sugimura Chemical Co., Ltd. was applied as a lubricant on both surfaces of the copper-plated steel sheet to prepare a test material. This test material blank is set in a die having a punch outer diameter Dp = 10.80 mm and a die inner diameter Dd = 10.00 mm so that the half punch diameter is 10 mm, and an autograph (compression mode) manufactured by Shimadzu Corporation. Was half-punched at an indentation speed of 5 mm / min and an indentation amount of 1.5 mm. At this time, Rp / t and Rd / t were changed to five types of 0.0, 0.04, 0.05, 0.06, and 0.07.

After the half-cutting process, the state of plating adhesion on the processed part side surface (punch side surface and die side surface) of the specimen was visually observed. Then, the evaluation was made by classifying the adhesion on the entire surface into three types: ◯, no partial plating Δ, and no plating ×. The results are shown in Table 1.
As can be seen from Table 1, when the punch R and the die R are set to 0.06 times or more with respect to the plate thickness t, it can be seen that plating failure does not occur on the side surface of the processed part after half-punching.

Example 2:
In Table 1, an indentation speed of 5 mm / min was applied to the test material half-punched under the condition of Test No. 19 from the state of (d) of FIG. 2 in an autograph (compression mode) manufactured by Shimadzu Corporation. Punching was performed in the direction opposite to half-punching under the condition of a pushing amount of 1.5 mm. At this time, Rp / t was changed to five types of 0.0, 0.04, 0.05, 0.06, and 0.07.
Then, after the punching process, the plating adhesion state on the processed part side surface (the side surface of the punched product A and the side surface of the punched product B shown in FIG. 3) was visually observed. The results are shown in Table 2. The evaluation criteria are the same as in Example 1.
As can be seen from the results in Table 2, after half-punching, if punching is performed with full punching under the condition that Rp / t is 0.06 or more, copper is applied to the entire side processing end faces of both punched product A and punched product B. The plating can be left.

Example 3:
Three types of cold-rolled steel sheets having a thickness of 1.0 mm, 1.6 mm, and 2.0 mm were used as materials, and a copper-plated steel sheet in which copper was electrodeposited on the surface with a film thickness of 3 μm was used. Using a punch and a die having the conditions of Test No. 19 in Example 1, the punching speed was 5 mm / min, and the punching amount was 94% of the plate thickness. Then, an autograph (compression mode) manufactured by Shimadzu Corporation was used. ), Punching was performed under the conditions of an indentation speed of 5 mm / min and an indentation amount of 1.7 mm. At this time, Rp / t was changed to five types of 0.0, 0.04, 0.05, 0.06, and 0.07.
Then, after the punching process, the plating adhesion state on the processed part side surface (the side surface of the punched product A and the side surface of the punched product B) of the test material was visually observed. The results are shown in Table 3. The evaluation criteria are the same as in Example 1.
As can be seen from the results in Table 3, punched product A and punched product B can be obtained by performing punching with all blanks under conditions where Rp / t is 0.06 or more, regardless of the thickness of the plated steel sheet. Copper plating can be made to remain on the entire side processing end faces of both.

The figure explaining the image of the plated steel plate punching process by the conventional method The figure explaining the image of the plating steel plate stamping process by this invention method Diagram explaining the punching type after punching

Claims (1)

Using a half-punching die with a punch shape of Rp / t ≧ 0.06 and a die shape of Rd / t ≧ 0.06 on a copper-plated steel plate of thickness t, a negative clearance is half-punched, and then The punch shape is the same diameter as the punch that has been subjected to half-punching processing, and a recess is formed in which the convex part that is half-punched is fitted into the tip surface, and a die with Rp / t ≧ 0.06 A method of punching a copper-plated steel sheet, characterized in that the copper plating remains on the entire surface of the punched end face by punching from the opposite direction.

Images