JP2001099113A - Mechanical joining method and material for plated steel sheet and painted steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanical joining method in which good appearance quality and high strength and durability are obtained at a joining portion, and a plated steel sheet and a coated steel sheet excellent in mechanical joining property used therefor. SOLUTION: In a mechanical joining method by caulking or rivet driving, mechanical joining is performed using a plated steel sheet and a coated steel sheet in which mechanical property values, plating and coating film thickness are specified as a material to be joined. [Effect] Using the plated steel sheet and the coated steel sheet of the present invention,
By performing mechanical joining, good appearance quality, high strength, and excellent durability can be obtained at the joint.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for mechanically joining coated steel sheets and painted steel sheets, which is used in a wide range of fields such as automobiles, home electric appliances, and building materials, and a coated steel sheet having excellent mechanical bonding properties. It relates to a painted steel plate.

[0002]

2. Description of the Related Art Plated steel sheets are currently used in a wide range of fields such as automobiles, home appliances, and building materials. In the fields of automobiles and home electric appliances, plated steel sheets are formed and joined to produce structures and parts. Spot welding is mainly used for joining these structures. This is because a high strength is obtained in the welded portion, the quality of the welded portion is stable, and the production cost is low. Spot welding is a very good method, but on the other hand, it has problems such as scattering (a phenomenon in which molten metal scatters around), fumes, and burning of oil during welding and odor. I have. In particular, recently, the so-called 3K workplace has been shunned, and in this sense, environmental issues in the production line have been taken up greatly, and a new joining method capable of joining plated steel sheets in a clean environment is desired. ing.

On the other hand, in the field of home electric appliances, there has been a demand to omit a coating process from the viewpoint of environmental problems, and there has been a movement to use a coated steel plate in which a coating is previously coated on the surface of the steel plate. Is coming out. However, in the case of painted steel plates, in many cases, the coating film has no conductivity, and thus it is difficult to join by spot welding that requires electricity. Further, even if the coating film has conductivity, there is also a problem that when the spot welding is performed, the coating film is destroyed by heat, thereby deteriorating the aesthetic appearance of the joined portion and deteriorating the corrosion resistance.

[0004] On the other hand, recently, it has been studied to use a mechanical joining method using caulking or driving rivets for joining a plated steel sheet or a painted steel sheet. 1 and 2
FIG. 2 is a view showing a typical mechanical joining method and the joining process. FIGS. 1A to 1D show the order in which plated steel sheets, which are materials to be joined, are joined by caulking. In the method shown in FIG. 1, two plated steel sheets 1 to be joined are overlapped with each other, a punch 2 is pushed in from above to deform the plated steel sheet with a die 3, and the two plated steel sheets are joined together. It is caulked and mechanically joined. As a specific method, the TOX method is known.

[0005] In Fig. 1, a die having a fixed shape is used. In addition to this, the die is divided into two parts. Some types are joined together. As a specific method, the Toglock method is known. The maximum strength of the joint is obtained by setting the swaged thickness 4 to an optimum value.

On the other hand, FIG. 2 shows a case in which plated steel sheets, which are materials to be joined, are joined together by rivet driving. In the method shown in FIG. 2, two plated steel sheets 1 to be joined are overlapped with each other, and a rivet 5 is driven from above with a punch 6.
Then, the tip of the rivet 5 is deformed as shown in the figure, and the two steel plates are mechanically joined to each other with rivets. 8 in the figure
Is a plate holder that prevents the plate from rising. Specific examples of this method include Henrob (Self piercing & rivetin
g) The method is known.

[0007] The mechanical joining method described above does not cause scattering or fume as in spot welding, and has no problems such as generation of odor. There are many expectations for a simple joining method. Also, in spot welding of plated steel sheets, the plating and the copper electrode undergo an alloying reaction during welding, the tip of the electrode wears out with an increase in the number of spots, the tip diameter increases, and the nugget (melted portion) due to a decrease in current density There is a problem that the diameter gradually decreases and the strength of the joint decreases. However, since such a problem does not occur in the mechanical joining method, a stable joining strength can be obtained even with about 50,000 hit points.

However, in the mechanical joining method using caulking or driving rivets as described above, the mechanical properties of the plated steel sheet or the coated steel sheet as the base material are large in the appearance quality, strength, and durability of the joint. affect. In other words, if a plated steel sheet or painted steel sheet with low formability (deformation ability) is used,
The thickness of the plated steel sheet or the like at the swaged or riveted part is reduced, or in extreme cases, cracks occur, resulting in impaired appearance quality of the joint or sufficient strength. There is a problem that there is no. In addition, corrosion occurs selectively in portions where the plate thickness is reduced or cracks occur, and as a result, the appearance quality is impaired or the strength is reduced in a short time.

On the other hand, in the joining method by caulking or riveting, the surface condition of the plated steel sheet or the coated steel sheet, that is, the thickness of the plating, the resin film, and the coating film has a great influence on the joining strength and corrosion resistance. In other words, if the plating and resin film of the appropriate thickness, the coating film is covered, plating and resin film, coating film remains at the joint even after mechanically joined,
The corrosion resistance of the joint is maintained, and the appearance quality is not impaired and the joint strength is not deteriorated even in a corrosive environment for a long time. In addition, plating or resin film of appropriate thickness,
If the coating film is coated, as described later, there is an advantage that the strength of the joint is improved as compared with the case of a bare steel plate which is not coated with the coating film.

[0010]

As described above, in the method of mechanically joining a plated steel sheet or a coated steel sheet, the thickness of the joint portion is reduced unless a coated steel sheet or a coated steel sheet having optimal mechanical characteristic values is used. It becomes thin and, in extreme cases, cracks occur, resulting in a problem that the appearance quality is impaired, a sufficient joint strength cannot be obtained, and the durability of the joint decreases. Furthermore, in the mechanical joining of plated steel sheets and painted steel sheets, if the plating, resin film, and coating film of the optimal thickness are not covered, the appearance quality is impaired due to corrosion, and sufficient durability is obtained at the joint. The problem that it cannot be performed arises.

The present invention is intended to solve such a problem, and proposes a mechanical joining method capable of producing a joint having excellent appearance quality, strength, and durability, and a machine used for the method. It is intended to provide a plated steel sheet and a coated steel sheet having excellent mechanical bondability.

[0012]

As an index indicating the formability of a plated steel plate and a coated steel plate, total elongation, work hardening coefficient (n
Value) and Rankford value (r value). Further, in general, the total elongation, the work hardening coefficient, and the Rankford value decrease as the tensile strength increases. Therefore, it is considered that the tensile strength also indirectly serves as an index indicating the formability. Therefore,
In order to prevent thinning or cracking at the mechanical joint of plated steel and painted steel,
It is desirable to use a plated steel sheet or a coated steel sheet in which these values are specified. In addition, in the mechanical joining of plated steel sheets and painted steel sheets, it is necessary to prevent plating, resin films, and coating films from peeling off during joining so that the appearance quality and durability of the joints are sufficiently maintained. . For this purpose, it is necessary to regulate the thickness of the plating, the resin film, and the coating film.

From such a viewpoint, the inventors of the present invention have conducted intensive studies in order to obtain good appearance quality and sufficient joining strength and durability at the mechanical joint of a plated steel sheet and a painted steel sheet. Good appearance quality at joints by mechanically joining by plating and riveting using plated steel sheet and painted steel sheet with defined mechanical property values, plating, resin film, and coating film thickness And sufficient strength and durability can be obtained.

That is, the gist of the present invention is as follows.
In the method of mechanically joining steel sheets by caulking or rivet driving, the mechanical properties of the base material are in the following range, and the basis weight of one side on the surface is 3 g / m.
^A machine using a coated steel sheet coated on both sides with a plating of ² or more and 150 g / m ² or less, or a coated steel sheet coated on both sides with a coating having a thickness of 5 μm or more and 100 μm or less on the plating. Mechanical joining of plated steel sheets or painted steel sheets, characterized by performing mechanical joining. 270 ≦ TS ≦ 480 30 ≦ El ≦ 45 0.18 ≦ n ≦ 0.27 (El: 5-15%) 0.70 ≦ r ≦ 2.2 (El = 15%) where TS: tensile strength ( MPa), El: total elongation (%), n:
Work hardening coefficient, r: Rankford value

Still further, the present invention is a plated steel sheet or a coated steel sheet used in a method of mechanically joining steel sheets by caulking or riveting, wherein the base metal has a mechanical characteristic value in the above-mentioned range and the surface thereof has A plated steel sheet excellent in mechanical bondability, characterized in that the plating of the basis weight is coated on both sides, or further characterized in that a coating film of the above thickness is coated on both sides of the plating. Painted steel sheet with excellent mechanical bondability.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, referring to the drawings, a method for mechanically joining a coated steel sheet and a coated steel sheet according to the present invention, and a plated steel sheet and a coated steel sheet having excellent mechanical bondability used in the method will be described in detail. Will be explained.

FIG. 1 and FIG. 2 are views for explaining a mechanical joining method according to the present invention. FIG. 1 (a) to (d)
Indicates the order in which the plated steel sheets as the materials to be joined are joined by caulking. In the method shown in FIG. 1, two plated steel sheets 1 to be joined are overlapped with each other, a punch 2 is pushed in from above to deform the plated steel sheet with a die 3, and the two plated steel sheets are joined together. It is caulked and mechanically joined. In FIG. 1, a fixed-shaped die is used. In addition, the die is divided into two parts, and when the die is pressed with a punch, it spreads right and left, and the plated steel sheets are joined together. Some are. The maximum strength of the joint is obtained by setting the swaged thickness 4 to an optimum value.

On the other hand, FIGS. 2 (a) and 2 (b) show the order in which plated steel sheets, which are materials to be joined, are joined by rivet driving. In the method shown in FIG. 2, the rivet 5 is driven from above by the punch 6 while the two plated steel sheets 1 as the materials to be joined are overlapped and pressed by the plate holder 8, and the rivet 5 is riveted by the die 7 when the rivet 5 is driven. 5 is deformed as shown in FIG. 2B, and the two plated steel sheets are mechanically joined to each other with rivets.

The plated steel sheet and the coated steel sheet used in the above-mentioned mechanical joining method may be those having the following mechanical characteristic values. 270 ≦ TS ≦ 480 30 ≦ El ≦ 45 0.18 ≦ n ≦ 0.27 (El: 5-15%) 0.70 ≦ r ≦ 2.2 (El = 15%) where TS: tensile strength ( MPa), El: total elongation (%), n:
Work hardening coefficient, r: Rankford value

By using a plated steel sheet and a coated steel sheet having the above-mentioned mechanical characteristic values, it is possible to prevent a reduction in the thickness of the joint portion and the occurrence of cracks. It is possible to obtain sufficient strength. Indices indicating the formability of the plated steel sheet and the coated steel sheet include the total elongation (El), the work hardening coefficient (n), and the Rankford value (r). Therefore, in order to prevent the plate thickness from becoming thin or cracking at the joint between the plated steel sheet and the coated steel sheet, the total elongation (El), the work hardening coefficient (n), and the Rankford value (r) are as described above. Must be greater than or equal to the value specified in. These mechanical property values are in the direction parallel to the rolling direction of the steel sheet (L direction) except for the r value.
And the average value of the measurements in the direction perpendicular to the direction (C direction). r
The value is generally called r bar, and when r values in a rolling direction, a direction perpendicular to the rolling direction, and a 45-degree direction are r _L , r _C , and r _D , respectively, (r _L + r _C +2
r _D ) / 4 in each direction.

On the other hand, the total elongation (El), the work hardening coefficient (n) and the Rankford value (r) are defined as the tensile strength (TS)
Therefore, it is considered that the tensile strength (TS) also indirectly serves as an index indicating the formability. Therefore, in order to prevent the sheet thickness from becoming thin or cracking at the joint portion of the steel sheet, the tensile strength (TS) needs to be equal to or less than the value specified above. On the other hand, in order to improve the formability, the total elongation (El), the work hardening coefficient (n) and the Rankford value (r) may be increased, but if these values become too large, the tensile strength (T
Since the value of S) decreases, the strength of the joint decreases. This is because the strength of the joint in the mechanical joining method is governed by the tensile strength (TS). Therefore, the total elongation (El), the work hardening coefficient (n), and the Rankford value (r) need to be equal to or less than the values specified above, and the tensile strength (TS) is specified above. It is necessary that the value be equal to or greater than the set value. The value indicating the strength of the plated steel sheet and the coated steel sheet has a 0.2% proof stress in addition to the tensile strength (TS), but the 0.2% proof stress of the plated steel sheet and the coated steel sheet used in the present invention. May be a value corresponding to the above-described tensile strength, total elongation, work hardening coefficient, and Rankford value.

The base material of the plated steel sheet and the coated steel sheet used in the present invention may be any type of steel sheet, such as a low carbon steel sheet, a solid solution strengthened steel sheet, and a precipitation strengthened steel sheet. The manufacturing method may be a hot rolling method or a cold rolling method. As a means for realizing the above-mentioned mechanical characteristic values, a method of appropriately combining the components, rolling reduction, annealing temperature, and the like can be adopted. In particular, the r value depends on the texture of the crystal orientation, but a high value can be realized by controlling the precipitated dispersed phase such as AlN. The plate thickness may be generally the thickness of a plated steel plate or a coated steel plate used in automobiles, home appliances, building materials, furniture, etc., specifically, a plate thickness of about 0.4 mm to 3.0 mm.

On the other hand, as the plated steel sheet used in the above-mentioned mechanical joining method, basis weight of the one side it is 3 g / m ² or more 150 g / m ² or less of plating may be a coated steel sheet coated on the surface. Further, a resin film having a thickness of 0.1 μm or more and 5 μm or less may be further coated on the plating. As a coated steel sheet, the surface area per side is 3g /
m ² or more 150 g / m ² or less of the plating is coated, further, the thickness on the said plating is 100μm or less of the coating film above 5μm may be used coated steel plate coated. Further, in the coated steel sheet, the thickness of the lower primer layer is 2 μm or more, the thickness of the upper top layer is 5 μm or more, and the total thickness of the primer layer and the top layer is 5 μm or more and 100 μm or more.
A coated steel sheet coated with the following coating film may be used.

The reason why the above-mentioned lower limits are set for the basis weight of the plating and the thickness of the coating film is that if a plated steel sheet or a coated steel sheet having a basis weight or a thickness of the coating film less than the above-mentioned lower limits is used, mechanical bonding is performed. In this case, the plating and the coating film at the joints are partially peeled off, exposing the steel sheet as the base material, and the appearance quality may be impaired, the durability may be reduced, and the strength of the joint may be reduced. Because there is. In addition, when a plated steel sheet or a coated steel sheet having a basis weight of plating or a coating film thickness exceeding the upper limit described above is used, plating or a coating film at a joint portion is easily peeled, so that appearance quality is impaired or durability is deteriorated. And the strength of the joint may be reduced. Therefore, by using a plated steel sheet or a coated steel sheet in which the thickness of the plating, the resin film, and the coating film is specified, the appearance quality and durability of the joint are kept good, and the strength of the joint does not decrease. It is. In terms of cost, unnecessary plating weight and coating film thickness are unnecessary. Further, when a plated steel sheet coated with plating in the above range is used, the strength and durability of the joint are improved as compared with the case where a bare steel sheet not coated with plating is used, and a resin is applied on the plated steel sheet. By coating the film or coating, the bonding strength and durability are further improved.

The plating type of the plated steel sheet used in the present invention includes Zn-based (Zn, Zn-Fe, Zn-Al, Zn-
Ni, Zn-Mg, etc.), Al-based (Al, Al-Si,
Al-Mn, Al-Mg, etc.), Pb-based (Pb-S
n, etc.). The plating method is hot-dip plating,
There are no particular restrictions on electroplating, thermal spraying, vapor deposition, and the like.

In the plated steel sheet coated with the resin film used in the present invention, the type of the resin film coated on the plating layer may be any resin such as polyester, epoxy, acrylic and urethane. Is also good. Generally, the resin film is coated after the chemical conversion treatment. The method of coating the resin film is not particularly limited.

The coating film of the coated steel plate used in the present invention may be any coating film used for a generally published coated steel plate. The coating film is composed of a top layer that is an upper layer and a primer layer that is a lower layer.The top layer may be any resin such as a polyester-based, epoxy-based, acrylic-based, or urethane-based resin, and a primer. Layers are polyester, epoxy, acrylic, urethane, etc.
Any resin may be used. The thickness of the coating film is 5 μm or more and 100 μm or less, but the thickness of the lower primer layer is 2 μm or more, and the thickness of the upper top layer is 5 μm or more,
Further, a coated steel sheet coated with a coating film having a total thickness of the primer layer and the top layer of 5 μm or more and 100 μm or less may be used. As the coating method of the coating film, brush coating, spray coating, bar coater coating, roller curtain coater,
Any method such as coating with a curtain flow coater or a roll coater may be used. Generally, the coating film is coated after the chemical conversion treatment.

The diameter and depth of the dies used for caulking shown in FIG. 1 are standard values used when joining a plated steel sheet or a painted steel sheet having the above thickness, specifically, the diameter is 3.0.
mm ~ 10.0mm, depth 0.5mm ~
What is about 2.0 mm may be used. The diameter of the punch may be appropriately selected according to the thickness of the material to be joined.

The rivet diameter (the diameter of a part to be driven into a steel plate) and length used for rivet joining shown in FIG.
What is necessary is just to select suitably according to the board thickness of a material to be joined. Specifically, the diameter is about 3.0 mm to 7.0 mm, and the length is 4.0 mm.
mm to about 14.0 mm may be used. The shape of the die may be any shape that does not cause cracking at the tip of the rivet. The material of the rivet may be any material having a 0.2% proof stress and a higher tensile strength than the material to be joined. This is because it is necessary to reliably punch the material to be joined with the rivet, and to prevent the rivet from breaking during a tensile test or a fatigue test.
Specifically, carbon steel for machine structures (S38C, S45C,
SK4, etc.) and stainless steel (SUS304, SUS4
30). However, when the rivet is deformed on the die side and joined by using a material having an excessively high 0.2% proof stress or tensile strength, a crack is generated in the rivet. It is preferable to use a rivet having a tensile strength.

[0030]

EXAMPLES (First Example) As the materials to be joined, the mechanical property values of the base material shown in Tables 1 and 2 (r value is the average (r bar) in each direction; 16 types of plated steel sheets (samples: No. 1 to No. 9, No. 11 to No. 12, sample types No. 1 to No. 9,
No. 14-No. 15, No. 17-No. 19) and three types of bare steel plates (No. 10, No. 13, No. 1)
6) was used.

[0031]

[Table 1]

[0032]

[Table 2]

As shown in FIG. 3, the shape is 30 × 100
A 0.8 mm test piece 9 (plated steel plate or bare steel plate) was wrapped by 30 mm wrap with a combination of similar materials, and as shown in FIG. 1, the overlapped portion was replaced with a punch having a diameter of 3.4 mm. 5.0mm in diameter, 1.0mm in depth
And mechanically joined. Note that the caulking thickness is set to 0.4 to 4 so that the strength of the joint 10 is maximized.
It was set between 0.6 mm. About these joints, the appearance of the joint was observed, and a tensile shear test based on the JIS tensile shear test method was performed. Further, a CCT test was performed on the joint based on the JIS corrosion test method, and after 4 weeks and 8 weeks, the appearance was observed and a tensile shear test was performed. The CCT test was performed under the conditions shown in the flowchart of FIG.

First, galvannealing (Zn-F
e) Regarding the results of the steel sheet, as a result of observing the occurrence of cracks on the die side of the test piece before the durability test,
In the case where the plated steel sheet having the mechanical property values of the present invention was used (No. 1 to No. 6), no crack occurred, but in the case where it was not (No. 16 to No. 19), Cracks had occurred.

In the case where plated steel sheets having a basis weight within the range of the present invention were used (No. 1 to No. 6), no peeling of the plating occurred at the joint portion. When a low plated steel sheet is used or when a plated steel sheet with a higher basis weight is used (Nos. 11 to 12,
No. 14-No. In 15), the plating at the joint was removed by friction at the time of joining, or the plating at the joint was peeled off, exposing the base material.

The tensile shear strength (TSS) of the joint before the durability test was measured. As a result, it was found that the joint was improved by coating with plating (No.
1 to No. 6 and no. 10, No. 13). On the other hand, when the appearance of the joint after the durability test and the tensile shear test were performed, joints using the plated steel sheet of the present invention (Nos.
o. In the case of 6), the corrosion of the joint was slight, and the tensile shear strength was slightly reduced even after 8 weeks, but otherwise (No. 10 to No. 19).
In Example 1, the corrosion of the joint was remarkable, and the tensile shear strength was remarkably reduced with time.

The type of galvanized steel sheet was changed to hot-dip galvanized (Z
n) Steel plate, electric Zn-Ni plated steel plate, hot-dip Zn-Al
The same experiment was performed instead of the plated steel sheet (No. 7 to N).
o. 9), but the result was the same as above. Similar results were obtained by using a plated steel sheet in which a 1.0 μm-thick polyester resin was coated on the surface of the plating. Further, an experiment was conducted by changing the thickness of the plated steel sheet, and the result was the same. A similar experiment was performed by mechanically joining the various test pieces shown in Tables 1 and 2 with a punch having a diameter of 4.57 mm and a two-part die having a diameter of 5.33 mm and a depth of 0.8 mm. In each case the results were the same.

(Second embodiment) The same test pieces as those of the first embodiment shown in Tables 3 and 4 were used as materials to be joined.
As shown in FIG. 3, these test pieces 9 (plated steel plate or bare steel plate) were overlapped by lapping them by 30 mm with a combination of similar materials, and as shown in FIG. A rivet 5 (material: S38C quenched material) having a length of 6.0 mm and a length of 6.0 mm was driven in from one side, and the rivet was deformed by a die 7 on the opposite side to be mechanically joined. The joints were evaluated for these joints in the same manner as in the first embodiment.

[0039]

[Table 3]

[0040]

[Table 4]

First, galvannealing (Zn-F
e) Regarding the results of the steel sheet, as a result of observing the occurrence of cracks on the die side of the test piece before the durability test,
When the plated steel sheet having the mechanical property values of the present invention was used (No. 20 to No. 25), no crack was generated, but when not (No. 35 to No. 38).
Had cracks.

When a plated steel sheet having a basis weight within the range of the present invention was used (No. 20 to No. 25), no peeling of the plating occurred at the joint portion. When a low plated steel sheet is used or when a plated steel sheet with a higher basis weight is used (No. 30 to No. 3)
1, No. 33-No. In 34), the plating at the joint was removed by the friction at the time of joining, or the plating at the joint was peeled off, exposing the base material.

The tensile shear strength (TSS) of the joint before the durability test was measured. As a result, it was found that the strength of the joint was improved by coating with plating (No.
20-No. 25 and no. 29, no. 32). On the other hand, when the appearance of the joint after the durability test and the tensile shear test were performed, the joint using the plated steel sheet of the present invention (N
o. 20-No. In the case of No. 25), the corrosion of the joint was slight, and even after 8 weeks, the tensile shear strength was slightly reduced.
-No. In No. 38), the joint was significantly corroded, and the tensile shear strength was remarkably reduced with the passage of time.

The type of galvanized steel sheet was changed to hot-dip galvanized (Z
n) Steel plate, electric Zn-Ni plated steel plate, hot-dip Zn-Al
The same experiment was performed instead of using a plated steel sheet (No. 26 to No. 26).
No. 28), but the results were the same as above. Similar results were obtained by using a plated steel sheet in which a 1.0 μm-thick polyester resin was coated on the surface of the plating. Furthermore, the experiment was conducted by changing the thickness of the plated steel sheet.
The results were the same.

(Third Embodiment) As materials to be joined, 13 types of coated steel plates (No. 39 to No. 44, No. .46-
No. 47, no. 49-No. 50, no. 52-N
o. 54) and three types of plated steel sheets (No. 45, No. 48, No. 51) not coated with a coating film.
In addition, the coating steel plate is made of three types of plated steel plates (No. 45,
No. 48, no. 51) was coated with a coating film having a different film thickness on top of the alloying molten zinc (Zn).
-Fe), and the basis weight per side is 40 g / m ² .

[0046]

[Table 5]

As shown in FIG. 3, the shape is 30 × 100
× 0.8mm test piece 9 (painted steel sheet or plated steel sheet)
Was wrapped by 30 mm in a combination of the same materials, and overlapped. As shown in FIG. 1, the overlapped portion was formed with a punch having a diameter of 3.4 mm, a diameter of 5.0 mm, and a depth of 1.0 m.
It was mechanically joined by caulking with a m die. Note that the caulking thickness is set to 0.4 to 4 so that the strength of the joint 10 is maximized.
It was set between 0.6 mm. The joints were evaluated for these joints in the same manner as in the first embodiment.

As a result of observing the state of occurrence of cracks on the die side of the test piece before the durability test, it was found that the coated steel sheet having the mechanical characteristic values of the present invention was used (No. 39 to No. 4).
In No. 4), no cracks occurred, but otherwise (Nos. 51 to 54), cracks occurred.

When a coated steel sheet having a thickness within the range of the present invention was used (No. 39 to No. 44), no peeling of the coating film occurred at the joined portion. When a thin coated steel plate is used or when a thick coated steel plate is used (Nos. 46 to 47, N
o. 49-No. In No. 50), the coating film at the joint was removed by friction at the time of joining, or the coating film at the joint was peeled off, exposing the base material.

The tensile shear strength (TSS) of the joint before the durability test was measured. As a result, it was found that the strength of the joint was improved by coating with a coating film over that of a plated steel sheet (Nos. 39 to 39). No. 44 and No. 45, No.
48 and comparison). On the other hand, when the appearance of the joint after the durability test and the tensile shear test were performed, the joint using the coated steel sheet of the present invention (No. 39 to No. 44) showed almost no corrosion at the joint, and after 8 weeks Also, the tensile shear strength did not decrease, but otherwise (Nos.
In No. 54), the joint was corroded, and the tensile shear strength decreased over time.

In the coated steel sheet, even if the type of the base coated steel sheet is changed to a hot-dip galvanized (Zn) steel sheet, an electric Zn-Ni plated steel sheet, or a hot-dip Zn-Al coated steel sheet,
By changing the basis weight of the base plating within the scope of the present invention,
Similar results were obtained. Further, an experiment was conducted by changing the thickness of the coated steel sheet, but the results were the same. A similar experiment was performed by mechanically joining the various test pieces shown in Table 5 with a punch having a diameter of 4.57 mm and a two-piece die having a diameter of 5.33 mm and a depth of 0.8 mm. Was the same.

(Fourth Embodiment) The same test piece as the third embodiment shown in Table 6 was used as a material to be joined. As shown in FIG. 3, these test pieces 9 (painted steel sheet or plated steel sheet) were wrapped with each other by 30 mm in a combination of the same kind of materials and overlapped, and as shown in FIG. A rivet 5 (material: S38C quenched material) having a length of 6.0 mm and a length of 6.0 mm was driven in from one side, and the rivet was deformed by a die 7 on the opposite side to be mechanically joined. The joints were evaluated for these joints in the same manner as in the first embodiment.

[0053]

[Table 6]

As a result of observing the state of occurrence of cracks on the die side of the test piece before the durability test, it was found that the coated steel sheet having the mechanical characteristics of the present invention was used (No. 55 to No. 6).
In No. 0), no cracks occurred, but otherwise (Nos. 67 to 70), cracks occurred.

Further, in this joining method, peeling of the coating film was observed at the joining portion in each case. However, when a coated steel sheet having a thickness within the range of the present invention was used (No. 55 to No. 5). 6
In the case of No. 0), the peeling of the coating film was relatively small, but when a coated steel plate having a thinner coating thickness was used or when a coated steel plate having a thicker coating film was used (No. 62 to No. 62). No. 6
3, No. 65-No. In No. 66), the coating at the joint was removed by friction at the time of joining, or the coating at the joint was peeled off, exposing the base material.

As a result of measuring the tensile shear strength (TSS) of the joint before the durability test, it was found that the strength of the joint was improved by coating with a coating film over that of a plated steel sheet (No. 55 to No. No. 60 and No. 61, No.
64). On the other hand, when the appearance of the joint after the durability test and the tensile shear test were performed, in the joint using the coated steel sheet of the present invention (No. 55 to No. 60), the corrosion of the joint was small and even after 8 weeks. , The tensile shear strength did not decrease, but otherwise (No. 61 to No. 70)
In, corrosion of the joint was observed, and the tensile shear strength decreased over time.

Even if the type of the coated steel sheet is changed to a hot-dip galvanized (Zn) steel sheet, an electric Zn—Ni-coated steel sheet, or a hot-dip Zn—Al coated steel sheet, the basis weight of the base steel sheet is not changed by the present invention. The same result was obtained by changing the value within the range. Further, an experiment was conducted by changing the thickness of the coated steel sheet, but the results were the same.

[0058]

According to the present invention, when the plated steel sheet and the coated steel sheet of the present invention are used for mechanical joining, high joint strength and excellent durability can be obtained at the mechanical joint.

[Brief description of the drawings]

FIGS. 1A to 1D are diagrams for explaining the order of a joining method by caulking in the present invention.

FIGS. 2A and 2B are diagrams for explaining the order of the joining method by rivet driving in the present invention.

FIG. 3 shows a tensile shear test piece.

FIG. 4 is a flowchart showing conditions of a CCT test.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 material to be joined 2 punch 3 die 4 swaged thickness 5 rivet 6 punch 7 die 8 plate holder 9 test piece 10 joint

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kanai 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Masahiro Ohara 20-1 Shintomi, Futtsu-shi, Chiba Made in New Japan Inside the Technology Development Division, Steel Corporation

Claims (4)

[Claims] 1. A method for mechanically joining steel sheets by caulking or riveting, wherein the base metal has a mechanical characteristic value in the following range, and the basis weight of one side of the base material is 3 g / m ² or more and 150 g or more. A mechanical bonding method for a plated steel sheet, wherein a mechanical bonding is performed using a plated steel sheet coated on both sides with a plating of not more than / m ² . 270 ≦ TS ≦ 480 30 ≦ El ≦ 45 0.18 ≦ n ≦ 0.27 (El: 5-15%) 0.70 ≦ r ≦ 2.2 (El = 15%) where TS: tensile strength ( MPa), El: total elongation (%), n:
Work hardening coefficient, r: Rankford value 2. A plated steel sheet used in a method of mechanically joining steel sheets by caulking or riveting, wherein the mechanical properties of the base material are in the range described in claim 1, and A plated steel sheet having excellent mechanical bondability, wherein both sides are coated with the plating having the basis weight according to claim 1. 3. A method for mechanically joining steel sheets by caulking or riveting, wherein the base metal has a mechanical characteristic value in the following range, and the basis weight of one surface of the base material is 3 g / m ² or more and 150 g or more. / M ² or less is coated on both sides, and the thickness of one side is 5
A mechanical bonding method for a coated steel sheet, wherein a mechanical bonding is performed using a coated steel sheet coated on both sides with a coating film having a thickness of at least 100 μm. 270 ≦ TS ≦ 480 30 ≦ El ≦ 45 0.18 ≦ n ≦ 0.27 (El: 5-15%) 0.70 ≦ r ≦ 2.2 (El = 15%) where TS: tensile strength ( MPa), El: total elongation (%), n:
Work hardening coefficient, r: Rankford value 4. A coated steel sheet used in a method of mechanically joining steel sheets by caulking or riveting, wherein the mechanical property value of the base material is in the range described in claim 3, and A mechanical joint comprising: a coating having a basis weight according to claim 3 coated on both sides; and a coating having a thickness according to claim 3 coated on the plating on both sides. Painted steel sheet with excellent properties.