TWI695746B - Surface-treated steel plate part with cut end face and its cut processing method - Google Patents

Abstract

The problem to be solved by the present invention is to provide a part with excellent corrosion resistance of a cut end face and a cut processing method thereof, which uses a surface-treated steel plate as a material and has a cut end face. In order to solve this problem, the part with excellent corrosion resistance of the cut end face of the present invention includes the cut end face of the surface-treated steel sheet after being cut, wherein the shape of the cut end face in the plate thickness direction The length of the first sag appearing is 0.10 times or more of the thickness of the surface-treated steel sheet, and the length of the second sag appearing in the plane direction is 0.45 times or more of the thickness of the surface-treated steel sheet. In addition, when the cutting process is performed, the cutting process is performed using a metal mold which sets the gap between the mold and the punch to 1 to 20% of the thickness of the surface-treated steel plate, and the mold A radius of curvature of 0.12 times or more of the thickness of the surface-treated steel sheet is provided on at least one shoulder of the punch and the punch.

Description

Surface-treated steel plate part with cut end face and its cut processing method

The present invention provides a part with excellent corrosion resistance of a cut end face and a cut processing method thereof. The part is used as a part for automobiles, home appliances, etc., which uses a surface-treated steel plate as a material and has a cut end face .

Previously, as parts used in automobiles, home appliances, etc., materials made of cold-rolled steel sheets were cut and plastic-processed into a predetermined shape, and then surface-treated, but in recent years, in order to improve the resistance of parts Corrosion, and omission of steps to reduce costs. These types of parts have gradually become mostly made of steel plates that have been surface-treated in advance (referred to as "surface-treated steel plates"), and the steel plates are cut and plastically processed. It was created to omit the surface treatment after plastic working. Here, when the surface treatment is applied after cutting and plastic working, since the surface treatment is also applied to the cut end surface at the same time, the cut end surface has the same corrosion resistance as the flat portion. On the other hand, when using a surface-treated steel sheet as a material and omitting the surface treatment steps after cutting and plastic working, the cut end face is directly exposed to the steel after cutting, so depending on the placement environment of the part, There may be rust (rust spots) on the cut end surface. Cutting off the rust on the end surface not only causes a poor appearance, but also the rust generation area will expand on the flat surface after the surface treatment is applied over time, so there is a concern that the strength of the part will be reduced, especially if it is in household appliances If there is rust falling on the product, there is a possibility of electrical short circuit.

For example, in Patent Document 1, there is proposed a method for improving the rust prevention ability of an end face after press working, which uses a metal mold to perform press processing on a Zn (zinc)-plated steel plate having a plate thickness of 2 mm or less. , Which has a radius of curvature of 0.1 to 0.5 times the thickness of the Zn-based plated steel plate on the shoulder of either the punch or the die, thereby making the ratio of the shear plane on the stamping end face after stamping 90% or more, and the coverage of the zinc layer on the shear surface should be 50% or more. In addition, Patent Document 2 proposes a method of making the shape of the cut end surface satisfy the following equation (1). t ² /(M‧Rs)≦0.2‧‧‧(1) where t is the plate thickness, M is the basis weight of Zn (the amount of adhesion per unit area), and Rs is the ratio of the shear plane.

[Prior Art Literature] (Patent Literature) Patent Literature 1: Japanese Patent No. 5272518 Patent Literature 2: Japanese Patent Laid-Open No. 10-280116

[Problems to be Solved by the Invention] However, in the method proposed in Patent Document 1 and Patent Document 2, only materials with a plate thickness of 2.0 mm or less are processed, even if they are intended to be applied to materials with a plate thickness of more than 2.0 mm, Rust may also occur due to insufficient coverage of the zinc layer on the shear surface, which may not be applicable. Therefore, the object of the present invention is mainly to provide a part capable of suppressing the generation of rust on the end surface after cutting processing even when a surface-treated steel plate having a plate thickness exceeding 2.0 mm is used as a material.

[Technical Means for Solving the Problem] The inventors conducted experiments and reviews in order to achieve the above object, and learned that the length and length of the first sag appearing in the thickness direction of the cut end surface early after the cutting process The length of the second sag that appears in the plane direction has a great influence on the rust on the end surface after cutting (hereinafter sometimes referred to as "cutting end surface"). Furthermore, the conclusion reached is that by controlling these values within a prescribed range, the generation of rust on the cut end face is suppressed, and the corrosion resistance can be greatly improved. The gist is as follows.

(1) A part having excellent corrosion resistance of a cut end face, which includes a cut end face of a surface-treated steel sheet after being cut, wherein the shape of the cut end face is first in the thickness direction The length of the sag is 0.10 times or more of the thickness of the surface-treated steel sheet, and the length of the second sag that appears in the plane direction is 0.45 times or more of the thickness of the surface-treated steel sheet, and the The surface is covered by the plated metal layer by being wrapped around the plated metal layer that has been coated on the surface of the surface-treated steel sheet.

(2) A cutting method is a method of cutting a surface-treated steel sheet using a metal mold composed of a die and a punch, wherein the metal mold used for cutting The gap between the heads is set to 1 to 20% of the thickness of the surface-treated steel sheet, and at least one shoulder of the die and the punch is provided with a radius of curvature of 0.12 times or more the thickness of the surface-treated steel sheet. In addition, the shape of the cut end surface after the cutting process has a length of the first collapse edge appearing in the plate thickness direction that is 0.10 times or more the thickness of the surface-treated steel sheet, and a second collapse edge appearing in the plane direction The length of the side is 0.45 times or more the thickness of the surface-treated steel sheet.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a part having excellent corrosion resistance of a cut end surface, even when a surface-treated steel sheet is used as a material, the cut end surface after cutting processing, Excellent corrosion resistance.

The inventors carried out experiments by varying the thickness of the surface-treated steel sheet, the conditions of the cutting process, the conditions of the surface treatment, etc. in various ranges, and investigated the relationship between the generation of rust on the cut end surface and the shape of the cut end surface, etc. . As a result, it is known that if the length of the sag at the cut end face is set, the length of the first sag is set to be within a range of 0.10 times or more of the plate thickness, and the length of the second sag is set to 0.45 of the plate thickness By performing the cutting process within a range of more than twice, it is possible to suppress the occurrence of rust on the cut end surface as the time after the cutting process elapses.

Here, the cutting process refers to cutting, punching, punching, etc. using shearing means. FIG. 2 schematically shows the cross-sectional shape of the steel plate after cutting. As shown in FIG. 2, the first edge 9, the second edge 10, the shear surface 11, and the broken surface 12 are formed on the cut end surface after the cutting process. Among them, the first sag 9 and the second sag 10 are sags formed by the tensile force acting on the surface of the steel plate as the punch moves toward the steel plate, and deforms the surface of the steel plate. In this specification, the first sag 9 appearing in the thickness direction of the steel plate is referred to as "sag Z", and the second sag 10 appearing in the plane direction is referred to as "sag X".

Under such conditions, the surface-treated steel sheet is sheared, whereby the tensile force applied to the steel sheet is increased together with the shearing force, so the plated metal layer covering the surface of the steel sheet material is wrapped to cut End face. In this way, by covering the plated metal layer, at least a part of the cut surface of the cut end surface is covered, and the covered plated metal layer has a sacrificial anticorrosive effect, so the generation on the cut end surface can be suppressed rust.

As shown in FIG. 3, the length L of the plated metal 8 wrapped around the cut end surface at this time is defined as the collapse edge Z(( The total value of the thickness of the first bead 9) and the length of the plated metal layer wrapped around the shear plane 11.

The upper limit of the length of the sag Z (first sag 9) and the sag X (the second sag 10) shown in FIG. 2 can be appropriately adjusted according to the thickness T of the steel plate and the conditions of the shear processing set up. Among them, the upper limit of the length of the sag Z is preferably 0.40 times or less the plate thickness, and more preferably 0.25 times or less the plate thickness. In addition, the upper limit of the length of the sag X is preferably 1.50 times or less the plate thickness, and more preferably 1.00 times or less the plate thickness.

According to the present invention, the shape of the cut end face is controlled in such a manner that the length of the sag is set within the aforementioned range, thereby promoting the deformation and movement of the plated metal due to the tensile force, so that the plated metal is oriented toward cutting The amount of wrapping on the end surface increases, so the area where the plated metal covers the cut end surface also expands. In this way, the initial corrosion resistance of the cut end surface can be improved. When the length of the sag is smaller, the deformation and movement of the plated metal become less, causing the plated metal to wrap around the cut end insufficiently.

Here, although the control of the length of the sag can be easily performed by changing the gap of the cutting tool and the radius of curvature of the shoulder of the mold, the cutting speed (pressing speed) that can be moved by the mold can also be used Wait for changes in conditions to proceed.

(Surface-treated steel sheet) As the surface-treated steel sheet used in the present invention, it is preferable to use a steel sheet to which a plating is applied on the surface. The plating here is exemplified by Zn-based, Zn-Al (aluminum)-based, Zn-Al-Mg (magnesium)-based, Zn-Al-Mg-Si (silicon)-based metal plating or alloy plating. Among them, it is preferable to use a steel plate to which Zn-Al-Mg-based alloy plating has been applied. Here, the alloy plating preferably contains 80% by mass of zinc relative to the total number of moles of plating, and more preferably contains 90% by mass or more.

Here, the lower limit of the coating adhesion on the surface-treated steel sheet is preferably 60 g/m ² , more preferably 90 g/m ² ; and the upper limit thereof is preferably 450 g/m ² , more preferably It is 190 g/m ² . In particular, if the adhesion amount of the plating on the surface-treated steel sheet is 90 g/m ² or more, the plated metal is easily wrapped around the cut end surface, so the corrosion resistance after shearing can be improved.

According to the present invention, even if a surface-treated steel plate having a large plate thickness is used, a part having excellent corrosion resistance at the cut end surface can be obtained. The thickness of the surface-treated steel sheet used for the cutting process can be appropriately set based on the shape, mechanical strength, weight, etc. of the parts to be produced. For example, even if a surface-treated steel plate with a thickness of more than 2.0 mm is used, the plated metal can be sufficiently wrapped around the cut end surface and the cut end surface can be covered, so the corrosion resistance after cutting can be improved.

(Cutting process) The cutting process of the surface-treated steel sheet can be performed using a metal mold composed of a die and a punch. Here, (a) and (b) of FIG. 1 show the state where the surface-treated steel sheet 1 is cut by the dies 2 and 3 (punch 2 and die 3). As shown in (a) and (b) of FIG. 1, the surface-treated steel sheet 1 held by the die 3 and the pressure plate 5 is sheared by the press-in of the punch 2, thereby obtaining the separated part 7 . At least one of the shoulder portion of the die 3 ((a) in FIG. 1) and the shoulder portion of the punch 2 ((b) in FIG. 1) is preferably formed into a curved shape having a radius of curvature.

If at least one of the shoulders of the die 3 and the punch 2 in the metal mold is bent into a portion in contact with the surface-treated steel plate, when the cutting process is performed, the steel plate will follow the shoulder or punch of the die 3 Since the shoulder portion of the head 2 is deformed, the steel plate is easily stretched in the plane direction and contributes to the increase of the sag X and the sag Z. Therefore, the radius of curvature imparted to the metal mold is preferably 0.12 times or more the thickness of the surface-treated steel sheet. For example, in the mold used in the example of the embodiment of (b) of FIG. 1, the shoulder portion of the punch 2 is formed into a curved shape. As the punch 2 is pressed in, the surface-treated steel plate on the side held by the die 3 and the pressure plate 5 is likely to cause the above-mentioned deformation of the steel plate surface, so the plated metal is wrapped around its cut end surface The situation is promoted, and a part 7 with good corrosion resistance at the cut end face can be obtained. The schematic diagram shown in FIG. 2 corresponds to the cut end surface of the component 7 at the right side of (b) in FIG. 1. When the metal mold shown in (a) of FIG. 1 is used, and the shoulder of the mold 3 is formed into a curved shape, the cut end surface of the part 7 falling on the punching side of the mold 3 is likely to produce the above The deformation of the surface of the steel plate is promoted, so that the wrapping of the plated metal is promoted, and a part 7 with good corrosion resistance of the cut end surface can be obtained.

In addition, the upper limit of the radius of curvature given to the metal mold is preferably 0.50 times or less of the thickness of the surface-treated steel sheet, and more preferably 0.30 times or less.

The gap between the die and the punch in the metal die is preferably 20% or less of the thickness of the surface-treated steel plate. With this, the shear force of the punch 2 against the steel plate can be increased, so the sag Z tends to increase. On the other hand, the gap between the die and the punch is preferably 1% or more of the thickness of the surface-treated steel sheet from the viewpoint that the steel sheet is easily stretched in the plane direction and the sag X is easily increased. , More preferably more than 3%.

The stamping speed of the metal mold for the surface-treated steel sheet can be set based on the gap between the die and the punch. The lower limit of the stamping speed is preferably 10 mm/s or more, and more preferably 20 mm/s or more. On the other hand, the upper limit of the stamping speed of the metal mold for the surface-treated steel sheet is preferably 200 mm/s or less, and more preferably 120 mm/s or less.

[Example]

The surface-treated steel plate used is a steel plate plated with Zn-6% by mass of Al-3% by mass of Mg alloy plating, and its plate thickness is 0.8, 1.2, 2.3, 3.2, 4.5, 6.0 (mm) The adhesion amount of plating is 90 or 190 (g/m ² ). For the cutting process, a square die 3 with a length of 40 mm on one side and a punch 2 whose side length is changed in accordance with the gap are used, and the surface-treated steel sheet 1 is held by the pressure plate 5. At this time, at least one of the shoulder portion of the die 3 and the shoulder portion of the punch 2 is formed into a curved shape given a radius of curvature 4.

The length of the sag Z and the sag X was measured for the shape of the part obtained by the shearing process. In addition, regarding the wrapping toward the cut end surface, the cross section of the central portion of the linear side portion of the part was observed with a microscope, and the length L of the plated metal wrapped around the end surface was measured in the thickness direction of the surface-treated steel plate . In addition, as shown in part 7 of (a) and (b) of FIG. 1, the measured sample is located on the opposite side of the mold or punch with curvature and is separated by cutting processing. Steel plate.

The part obtained by performing the cutting process was placed outdoors to perform an atmospheric exposure test, and the number of days until the generation of conspicuous rust was observed on the cut end surface was 15 days. The results are shown in Table 1. In Table 1, the conditions of the surface-treated steel plate used for each part, cutting processing, etc. are shown together. Here, the radius of curvature (plate thickness ratio) of the metal mold is obtained by dividing the plate thickness by the radius of the arc given to the shoulder of the mold 3 or the shoulder of the punch 2. Dies or punches that are deliberately not given an arc are marked as "<0.01" in this column and as "none" in the column of "Metal Dies with Curvature Given". In Example 13 of the present invention, a circular arc with a radius of curvature of 0.14 is given to both the die and the punch.

As shown in Table 1, it corresponds to Inventive Examples 1 to 15 of the present invention, and the length of the sag Z appearing in the thickness direction is 0.10 times or more the thickness of the surface-treated steel plate and appears in the planar direction The length of the sag X is 0.45 times or more the thickness of the surface-treated steel sheet. The cut end face exhibits good corrosion resistance that will not produce rust until 90 days or more. In addition, in Examples 1 to 15 of the present invention, the ratio of the wrapping length L ([B]) of the plated metal of the plate thickness ([A]), that is, the value of [B]/[A] is 0.30 or more Higher range.

In contrast, in Comparative Examples 1, 2, 4, and 5, the sag Z is less than 0.10, so the number of days until rust occurs on the cut end surface is less than 90 days. Compared to the present example, Comparative Examples 1, 2, and 4 , 5 has poor corrosion resistance. It is presumed that this is because these comparative examples have no arc (curvature) provided on the metal mold, resulting in a decrease in the sag Z.

In Comparative Example 3, the sag X was less than 0.45, so the number of days until rust occurred on the cut end surface was less than 90 days. Compared with the example of the present invention, Comparative Example 3 had poor corrosion resistance. Also, in Comparative Examples 1 to 5, the ratio of the wrapping length L of the plated metal to the plate thickness, that is, ([B]/[A]) is in the range of less than 0.30.

Based on the above description, it was confirmed that the length of both of the sag Z and the sag X in the shape of the cut end face is set to a predetermined range or more, whereby a cut end face having good corrosion resistance can be obtained.

[Table 1]

1: Surface treated steel plate

2: punch

3: mold

4: The radius of curvature given to the shoulder of the die or the shoulder of the punch

5: pressure plate

6: clearance

7: Parts

8: plating metal layer

9: Collapse Z (First Collapse)

10: Collapse X (Second Collapse)

11: shear plane

12: Broken section

L: wrapped length of plated metal

T: Thickness

Fig. 1 is an embodiment of the cutting process of the present invention, wherein (a) is a schematic diagram illustrating a cutting process method in which a radius of curvature is given to a shoulder of a die, and (b) illustrates a shoulder on a punch A schematic diagram of a cutting method with a radius of curvature given to the part. FIG. 2 is a schematic cross-sectional view for explaining the sag Z and the sag X of the cut end surface. FIG. 3 is a schematic cross-sectional view for explaining the length L of the plated metal wrapped around the cut end surface.

Domestic storage information (please note in order of storage institution, date, number) No

Overseas hosting information (please note in order of hosting country, institution, date, number) No

(Please specify separately on page change)

1‧‧‧Surface treated steel plate

7‧‧‧Parts

9‧‧‧collapse Z (first collapse)

10‧‧‧collapse X (second collapse)

11‧‧‧Shear plane

12‧‧‧broken section

T‧‧‧Thickness

Claims (4)

A part having excellent corrosion resistance of a cut end face, which includes a cut end face of a surface-treated steel sheet after being cut, wherein the shape of the cut end face, which appears in the thickness direction of the first sag The length is 0.10 times or more and 0.40 times or less the thickness of the surface-treated steel plate, and the length of the second sags appearing in the plane direction is 0.45 times or more and 1.50 times or less the thickness of the surface-treated steel plate, and, The surface of the aforementioned cut end face is covered with the plated metal layer by being wrapped around the plated metal layer that has been coated on the surface of the surface-treated steel sheet. The part having excellent corrosion resistance of a cut end surface according to claim 1, wherein the surface-treated steel plate is a zinc-plated steel plate. A cutting processing method is a method of cutting a surface-treated steel plate using a metal mold composed of a mold and a punch, wherein the metal mold used for cutting cuts between the mold and the punch The gap is set to 1-20% of the thickness of the surface-treated steel plate, and at least one shoulder of the die and the punch is provided with a radius of curvature of 0.12 times or more of the thickness of the surface-treated steel plate. The shape of the cut end surface after the breaking process, the length of the first sag edge appearing in the thickness direction is 0.10 times or more and 0.40 times or less the thickness of the surface-treated steel sheet, and the second appearance in the plane direction The length of the sag is 0.45 times or more and 1.50 times or less the thickness of the surface-treated steel sheet. The cutting method according to claim 3, wherein the surface-treated steel sheet is a zinc-plated steel sheet.

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