JPS6046015B2 - weldable laminates - Google Patents

Description

[Detailed description of the invention] The present invention relates to weldable laminates.

A laminate with a three-layer structure in which a thermoplastic synthetic resin material is sandwiched between two metal plates can be used in a wide range of applications such as automobiles, building materials, home appliances, and other structures. This is because such a laminate is lighter than a single plate, and can ensure higher rigidity with the same weight. Thermoplastic synthetic resins used for laminates include polypropylene, polyolefin, polyester, and various other resins, but all of these resins are electrical insulators, and the thickness of this resin is also small. They are usually considerably larger than metal plates.

For this reason, resistance welding such as spot welding is completely impossible for laminates, and they must be joined by bolts or adhesives during assembly, which is a big disadvantage in terms of workability and assembly costs. However, due to this disadvantage, the applications of laminates are severely restricted. The object of the present invention is to improve the greatest weakness of laminates, which is that they cannot be welded, and to expand their uses.

That is, the present invention relates to the structure of a laminate,
The feature of this laminate structure is that, as shown in the longitudinal cross-sectional side view of FIG. The convex portions are in contact with each other through the synthetic resin layer.

A laminate having such a structure can be subjected to resistance welding such as spot welding.

In other words, the laminate of the present invention can naturally be used to overlap two laminates and spot weld the contact points of the metal plates (indicated by the symbol A in FIG. 1). Instead, it is also possible to spot weld a portion apart from the contact point A, that is, a portion B where a synthetic resin material is interposed between the two metal plates 2, 2. As shown in FIG. 2, when two laminates 1 of the present invention are stacked one on top of the other, and the point where the B portions overlap is sandwiched between electrodes 6, 6 and pressurized, and a voltage is applied between both electrodes, A current flows through the A part in the vicinity and heats the metal plates 2, 2, and as a result, the synthetic resin material in the B part of both laminates softens and finally disappears by vaporization. By applying the pressure, the four surface metal plates 2 come into direct contact with each other, resulting in the formation of a nugget 7 spanning between the four metal plates. Since the structure of the present invention uses a metal plate with a convex pattern, the convex pattern can be expected to act as reinforcement, and is also effective in improving the rigidity of the laminate.

In addition, compared to the conventional flat plate, the contact area between the synthetic resin layer 3 and the metal plate 2 increases by the presence of the convex portion, so the structure of the present invention is advantageous from the viewpoint of ensuring peel strength. In fact, it can be said to be a good idea. Needless to say, as the metal plate 2 of the laminate of the present invention, any material that can be resistance welded, such as a steel plate, can be used.

The protrusions may be formed on the metal plate by normal embossing. Also, for the synthetic resin layer 3, any of the various thermoplastic resins conventionally used in this type of laminate may be used.

Examples include thermoplastic polyester, vinyl chloride, acrylic resin, methacrylic resin, cyanoacrylate, polyamide, polyether, adhesive polyolefin, and modified products and composites of these resins. In the laminate of the present invention, the shape of the convex portions 4 of the metal plate is not particularly limited.

However, if we consider the manufacturing aspect, the convex portion 4 is the 1st. As shown in FIG. 3, it is preferable to form continuous or discontinuous protrusions 5 that are regularly arranged in parallel, and to form the tops 5'' of the protrusions into a rounded shape.In other words, the laminate of the present invention can also be processed as usual. Two metal plates and a synthetic resin sheet are crimped under heat using a press molding machine, or resin is supplied in sheet form between two metal plates from a melt extruder and this is crimped with a roll. Although it may be manufactured by any method, in the laminate of the present invention, it is an essential condition that the convex portions of both metal plates are in contact with each other through the synthetic resin layer. When using the above method, as shown in FIG. 4, the resin 3'' between the protrusions 4, 4 of both metal plates is removed as the crimping progresses, and eventually the protrusions 4, 4 are removed. Care must be taken to ensure that the metal plates are in complete contact with each other, and at the same time, that the corresponding convex portions of both metal plates are matched without fail. The parallel protrusions 5 shown in FIG. 3 above are designed to address this problem. That is, two metal plates on the front and back sides having such parallel protrusions 5 are placed facing each other so that the protrusions intersect with each other as shown by the solid line a and the broken line b in FIG. 5 when viewed from above, In other words, if used as shown in FIG. 3, even if the two metal plates are slightly misaligned from the original plan during crimping, the protrusions 5, 5 will always correspond to each other. At the same time, since the tops 5'' of the protrusions have a rounded shape, the removal of the resin 3'' (see Figure 4) between both protrusions can be achieved very smoothly, and as a result, the protrusions on both metal plates It becomes possible to always stably obtain the laminate of the present invention in which the parts are in contact with each other through the resin layer. The height (H) of the convex portion of the metal plate 2 (see FIG. 3) is most preferably in the range of 1.5 to 2 times the plate thickness (t).

That is, this type of laminate is generally used after being subjected to bending, drawing, stretching, and the like. On the other hand, it is common sense and advantageous to form convex portions on a metal plate by rolling (rolling with an embossing roll), but the above H/t is 2
．． When the thickness exceeds 5, the reduction in wall thickness due to processing becomes large when forming convex portions by rolling, and in this case, the above-mentioned various formability as a laminate is significantly reduced. This H again
If /t is less than 1.5, the thickness of the resin layer interposed between the two metal plates must be reduced because in the case of the laminate of the present invention, the convex portions of the front and back metal plates must be in contact with each other. , the inherent weight reduction advantage of the laminate will be lost. The thickness (T) of the laminate of the present invention is the height of the convex portion (H) of the metal plate used.
) is roughly determined by In order for the convex parts of both metal plates to contact each other, it is necessary that the thickness (T) of the laminate is less than or equal to the sum of the heights (H) of each convex part of both metal plates. If it is too small, the convex portions 4, 4 of both metal plates will be significantly crushed and deformed, and the thickness T) of the laminate will become thinner, which is not preferable. It should be noted that the metal plates used in the laminate of the present invention do not necessarily have to have the same thickness or convex pattern, but the thickness of the front and back metal plates and the convex pattern may vary depending on the application. Needless to say, it is possible to have different patterns.

Further, while the metal plate of the laminate of the present invention requires a convex pattern on the synthetic resin layer side, the outer surface may be flat or have concave portions. Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Using a cold rolled steel plate with a thickness of 0.2 mIn, by embossing, the height of the protrusion (H) 0.43wrm1 the width of the protrusion (W)2 order, the pitch (P) 57r$t1 the running direction of the protrusion An embossed plate was obtained in which the angle was inclined by 307 degrees with respect to the longitudinal direction of the steel plate.

These two embossed plates were placed facing each other as shown in FIG. 3, and a polypropylene sheet was sandwiched between them and pressed together under heat using a press machine to obtain a laminate having a thickness of 0.8 rf0fL. Using this laminate, spot welding is carried out,
Resistance weldability was investigated.

For spot welding, as shown in Fig. 2, the 12 laminated plates described above are superimposed, and an electrode 6 with a tip diameter of 6=4-8,
6 under the conditions shown in Table 1. The above welding is
After welding, the tensile strength of the welded area was investigated at both the point A1 where the convex parts of both metal plates were in contact and the other point B.

For comparison, two cold-rolled plates with a thickness of 0.4T0n were spot welded under the same conditions, and the tensile strength was examined. The results are summarized in Table 2.

In the above table, the test results of the present invention example are the points A and B.
The test was conducted 10 times at each point and the average was calculated, but no significant difference was observed between the test results at point A and point B.

The tensile strength after welding in the inventive example can be made sufficiently good, with no significant difference seen compared to the comparative example using a general cold-rolled plate. Next, the peel strength between the metal plate and the synthetic resin layer in the above-described laminate of the present invention was investigated.

The peel test is a T-type peel test 2 according to JISK6854.
It was carried out at 0'C. The results are shown in Table 3. The same table also shows, as a comparative example, the peel strength of a normal laminate with a total thickness of 0.8 Tm in which polypropylene is sandwiched between two cold-rolled sheets of 0.2 T1rIn. From the results in Table 3, it can be seen that the laminate of the present invention has a good peel strength that actually exceeds that of a conventional laminate.

This is because, as mentioned earlier, in the laminate of the present invention, the convex portions of the two metal plates are in point contact with each other, and the bonding area is large due to the small contact area between the metals. This is because the contact area between the metal plate and the resin layer increases because the plate has the convex portion. Example 2 The results of an investigation into the relationship between H/t (see FIG. 3) and formability in the laminate of the present invention are shown as A in FIGS. 6 to 8.

This test was carried out using the laminate of the present invention under the following conditions, bending, drawing (100T! UrLf circular drawing) and stretching (1
00Tm! We conducted three types of tests (RLf ball head overhang) to investigate the limit bending radius (outside) without cracking, the limit drawing ratio, and the limit overhang height, and plotted the above values on the vertical axis. , H/t is plotted on the horizontal axis. In the figure, the thickness (T) of the laminate itself is also displayed as the horizontal axis. Note that here, the thickness (T) of the laminate and H/t correspond to T = 2 x H/t x t (t = 0.27 m here), but in reality, the laminate of the present invention In this case, the thickness of the laminate (T) is smaller than the value of 2×H because a contact distance between the convex portions of the front and back metal plates is required. However, the laminate of the present invention tested here was
This contact fee is 51,100Tm! This was ignored here because it was assumed to be extremely small, about n. Tested laminate of the present invention> Front and back metal plates: 0.2TIUf1 thick cold-rolled steel plate for drawing (SPCD) with a convex pattern provided by embossing, t=0.2TI$ shown in Figure 3 T. ．． W
=2wn1P=5? , with various changes in H.

Synthetic resin layer: polypropylene Manufacturing method: Press under heat using a press machine.

In addition, for comparison, the same test was carried out on a conventional laminate plate under the same conditions as above, except that the front and back metal plates are 0.2770 ft thick cold-rolled steel plate for drawing without embossing as B. The results obtained are also shown. This is shown in correspondence with the above A in terms of the thickness (T) as a laminate. Needless to say, the smaller the limit bending radius shown in FIG. 6 is, the larger the limit drawing ratio and limit overhang height shown in FIGS. 7 and 8 are.
There are some indications that the moldability is better.

From the test results shown in FIGS. 6 to 8, the laminate of the present invention can be bent, drawn, and
It is clear that in any of the stretching processes, it shows good formability on the same level as a general laminate.

As is clear from the above description, the laminate of the present invention is
Resistance welding is possible, and it also has the advantage of being superior to conventional products in terms of interlayer peel strength and rigidity, and is almost as good as conventional products in terms of formability. , it can be said that it has a great effect.

[Brief explanation of drawings]

FIG. 1 is a vertical side view showing the basic structure of the laminate of the present invention;
Fig. 2 is a front view showing a state in which two of the same laminated sheets are spot welded, Fig. 3 is a perspective view showing a preferred example of a metal plate used in the laminate of the present invention, and Fig. 4 is a heating of the laminate of the present invention. FIG. 5 is a plan view for explaining a preferred example of the laminate of the present invention, and FIGS.
The figure shows the results of a comparison of the formability of the (10) laminate of the present invention and a conventional product. In the figure, 1: laminate of the present invention, 2: metal plate, 3: synthetic resin layer, 4: protrusion, 5: protrusion, 6: electrode, 7: nugget.

Claims (1)

[Scope of Claims] 1. A laminate comprising a thermoplastic synthetic resin layer interposed between two metal plates, each of which has a convex pattern protruding toward the synthetic resin layer, A weldable laminate, characterized in that the convex portions of both metal plates are in contact with each other through a synthetic resin layer. 2. A patent claim characterized in that the protrusions provided on the metal plates are regularly juxtaposed protrusions, and the directions of the protrusions on both metal plates are different from each other and the metal plates are in point contact with each other. A weldable laminate according to item 1.