JPH05329665A - Production of composite metallic plate having excellent joint strength - Google Patents

Abstract

PURPOSE:To obtain the composite plate having good joint strength by heating an iron plate and an aluminum plate to the temp. respectively within specific ranges, superposing these plates on each other and applying external force thereto from both surfaces, thereby increasing the thickness decreasing rate of the aluminum layer to a specified value or above. CONSTITUTION:The composite metallic plate consisting of three layers; the iron for both front surfaces and the aluminum for the center or the composite metallic plate consisting of two layers; the iron for one surface and the aluminum for the other surface is produced. The iron layer is heated to 670 to <=1050 deg.C for the, purpose and the aluminum layer is heated to <=550 deg.C. The plates are superposed in each other when both layers are in these temp. ranges. The external force is applied thereto immediately from both surfaces to increase the thickness decreasing rate of the aluminum layer by the external force to >=2% of the thickness of the aluminum layer before the external force is applied thereon. The plates are thereafter allowed to cool or are forcibly cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is suitable for use as a material of a structure that requires the application of both iron and aluminum structurally, or as a material for joining both iron and aluminum.

[0002]

2. Description of the Related Art The weight reduction of thin steel sheets used as structural materials for automobiles has been a major issue, and various means have been proposed. One way to reduce the weight is to use aluminum partially. Many structures that use aluminum also use iron materials at the same time, and joining them is an issue. Generally, it is difficult to weld iron and aluminum, and a method of mechanically joining them with a rivet is often used. However, this method has problems such as poor productivity, poor weight reduction rate due to the necessity of overlapping the joints, and poor appearance. In order to solve these problems, it is conceivable to use a composite metal plate in which iron and aluminum are preliminarily joined at the joining portion of iron and aluminum, and to join the same metals.
Therefore, a metal thin plate in which iron and aluminum are strongly bonded beforehand has been desired.

Conventionally, various methods have been devised as a method for joining an iron plate and an aluminum plate.
As disclosed in Japanese Patent Publication No. 157774, a method of heating an aluminum material to about 350 to 550 ° C. and rolling and joining with an iron material in a warm state, as disclosed in Japanese Patent Publication No. 56-52679. There is a method in which aluminum is plated on the surface in advance, and this is heated to about 500 ° C. and hot-rolled with an aluminum material to join them.

However, these methods have a problem in that the strength of the joint interface between iron and aluminum cannot be sufficiently high. For example, as shown in the example of Japanese Examined Patent Publication No. 56-52679, although it does not peel off in a process such as a slight bend such as 180 ° bending once, it does not peel in a press process such as bending and unbending. It cannot be said that it has sufficient bonding strength. In each of the above publications, the aluminum portion of aluminum or an aluminum-plated steel sheet is heated, and the joining is mainly performed by diffusion of aluminum atoms. There is a drawback that it is difficult to obtain a strong interfacial strength because the mutual diffusion with the iron material is insufficient only by diffusing only aluminum. Further, it is not preferable to use a plate made of iron plated with aluminum as a raw material as in Japanese Patent Publication No. 56-52679, because it causes an increase in cost. As described above, a method for producing a composite plate of iron and aluminum having a strong bonding strength that can withstand use as a structural material has not been known so far.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for producing a composite plate of iron and aluminum having a strong joint strength.

[0006]

In order to solve the above-mentioned problems, the present inventors have examined the temperature and plate thickness reduction rate of each metal in the case of bonding by applying an external force, and as a result, found that good bonding strength was obtained. A method of manufacturing a composite plate of iron and aluminum has been found. That is, the gist of the invention is that when a composite metal plate having three layers of iron on both surfaces and a center of aluminum, or a composite metal sheet having two layers of iron on one side and aluminum on one side is manufactured, the iron layer is 670 ° C or higher. The aluminum layer is heated to 1050 ° C. or lower, the aluminum layer is heated to 550 ° C. or lower, and when all the layers are in these temperature ranges, the layers are superposed, and an external force is immediately applied from both surfaces to reduce the plate thickness reduction rate of the aluminum layer by the external force. It is a method for producing a composite plate having excellent bonding strength, which is characterized in that the plate thickness of the aluminum layer before addition is 2% or more, and then it is allowed to cool or forcedly cool.

[0007]

In the present invention, both the iron material and the aluminum material may be cold rolled or annealed. The reason is that the iron material recrystallized by heating the iron material applied in the present invention and softened even in the cold rolled material. Further, according to the investigation by the present inventors, the bonding strength of the composite plate is affected by the temperature condition and the reduction rate of the plate thickness of the aluminum layer, so that the aluminum material is cold-rolled or after recrystallization. It does not matter in particular whether the material is.

The present invention will be described in detail below. The iron material may be manufactured by a normal hot rolling or cold rolling process. Further, either a cold rolled steel sheet or an annealed steel sheet may be used, and the composition is not particularly limited. The as-cold-rolled iron material is sufficiently softened when heated to 670 to 1050 ° C., which is the heating range of the present invention, so that it is possible to obtain a material that sufficiently withstands bending and pressing when used as a structural material. Be done. Further, even if the iron material has already been annealed, there is no problem due to heating within the range of the present invention.

Next, the aluminum material may be pure aluminum or aluminum alloy.
Hereinafter referred to as an aluminum layer. When joining these iron and aluminum materials, mechanical strength by external force without heating the materials, or joining only when the aluminum part is heated to about 500 ° C is not sufficient for joining strength. The present invention is a method of heating and diffusing each of iron atoms and aluminum atoms to bond them. At this time, when an alloy layer is formed at the joint interface, it becomes brittle, so that the formation of the alloy layer is suppressed, and the atoms of iron and aluminum are diffused into each other to obtain a large joint strength. First,
The iron layer should be heated to a minimum of 670 ° C. This temperature is necessary for the atoms of the iron layer and the aluminum layer to diffuse when they are brought into contact with each other to form a diffusion layer.
However, when heated to a temperature higher than 1050 ° C., a brittle alloy layer is likely to be formed at the bonding interface during bonding with an aluminum plate, and the bonding strength is reduced. Therefore, the heating temperature of the iron plate before joining was set to 670 to 1050 ° C.

Next, when the iron plate is heated to the above temperature at the time of joining, the aluminum layer can obtain good joining strength without being particularly heated. This is because when the iron layer and the aluminum layer are superposed on each other, the heat from the iron layer is also applied to the aluminum layer, and the temperature becomes a temperature at which aluminum atoms can also diffuse. The aluminum layer may be either an as-cold-rolled plate or an annealed plate, but when cold-rolled aluminum is used as a material, the aluminum layer may be soft-annealed depending on the application. The heating temperature of the aluminum layer in this case must be 550 ° C. or lower. If this temperature is exceeded, heat from the iron layer is also added to the temperature of the aluminum layer itself, so that aluminum may melt at the bonding interface when superposed, and the bonding strength is significantly reduced.

After heating the iron layer and the aluminum layer to the above temperature range, it is necessary to immediately apply an external force by superposing the respective metals when the temperature is within this temperature range. Sufficient bonding strength cannot be obtained when the layers are stacked at a temperature outside the above temperature range.

Next, the reduction rate of the plate thickness of the aluminum layer due to the external force required for joining will be described. In order to join the iron layer and the aluminum layer, after overlapping the respective materials in the temperature range described above, apply external force from both sides of the composite plate, and before applying the external force to the aluminum layer thickness reduction rate due to the external force. 2% or more with respect to the plate thickness of the aluminum layer. FIG. 1 shows that when a composite plate having an aluminum plate at the center and iron plates on both sides is manufactured, the iron plate and the aluminum plate are heated to 820 ° C. and 300 ° C., respectively, by the equipment as shown in FIG. Bonding strength (T
It shows the plate thickness reduction rate of the aluminum layer that affects the mold peeling strength). As is clear from FIG. 1, the bonding strength becomes stronger as the plate thickness reduction rate of the aluminum layer due to the external force increases, and particularly at 2% or more, the bonding strength becomes good. Similar results were obtained when the respective heating temperatures were changed within the range of the present invention and when a composite plate composed of two layers, one side being an iron layer and one side being an aluminum layer, was joined. Further, according to the investigation by the present inventors, it is known that the reduction rate of the iron layer thickness due to the external force at the time of joining does not particularly affect the joining strength.

In the electric heating and pressure welding equipment shown in FIG. 2, electric current rolls 11, 13 and 12 are provided on the iron layers 1 and 3 and the aluminum layer 2 of the material, respectively. The composite plate 5 is manufactured by continuously feeding it between the rolls 4. As the power source, either a low frequency AC power source or a DC power source can be used. The current of the power source 21 passes through the iron layer 1 from the energizing roll 11 through the iron layer 1 and the aluminum layer 2 to reach the energizing roll 12. Similarly, the current of the power supply 22 flows through the series circuit of the aluminum layer 2 and the iron layer 3. In the case of alternating current, if the phases of the two power supplies 21 and 22 are properly matched, the current of the aluminum layer 2 becomes the sum of the currents from the two power supplies. In this case, since the iron layer has a higher electric resistance than the aluminum layer, if the iron layer and the aluminum layer have the same thickness, the iron layer generates more heat and becomes hot. If the heating temperature of the iron layer does not reach the target temperature, the auxiliary heating is performed by energizing the energizing rolls 14 and 15 provided for auxiliary heating from the auxiliary heating power sources 23 and 24, respectively.

The joining of the plates is instantaneously performed under the above-mentioned conditions, but if kept at a high temperature after the joining, a brittle alloy layer is formed at the interface between iron and aluminum and the joining strength is lowered.
Therefore, the composite board must be cooled quickly. The cooling rate may be a rate that can be obtained by standing cooling, but in order to further shorten the cooling time, forced cooling by gas or liquid may be used.

When joining an iron layer and an aluminum layer,
The joining method is not particularly limited as long as the above joining conditions can be satisfied, and a method of applying an external force between two rolls as shown in FIG. 2 or a method of pressing may be used.
The method for heating the joining material may be any method such as electric heating or heating with a heating furnace.

By joining the iron plate and the aluminum plate by the method as described above, a composite plate of iron and aluminum having excellent joining strength can be manufactured. Hereinafter, examples of the present invention will be shown together with comparative examples.

[0017]

[Example 1] Using an iron layer and an aluminum layer as shown in Table 1 as raw materials, a heating temperature and a plate thickness reduction rate as shown in Table 1 were used for the center of the aluminum layer and both sides of the iron layer. The three-layer composite plate was joined and allowed to cool. The aluminum layer used pure aluminum and various aluminum alloys as a joining material. These materials were wound in a coil shape, and they were continuously heated by an apparatus as shown in FIG. 2 while unwinding the coils before joining. Overlap immediately after heating,
External force was applied from both surfaces. The external force was applied by the two rolls shown in FIG. 2 to join the plates continuously. The composite plate after joining was immediately forcibly cooled with gas at 15 ° C./s.

[0018]

[Table 1]

Sample Nos. 1 to 12 are within the scope of the present invention in terms of composition and bonding conditions, and Sample Nos. 13 to 20 are out of the scope of the present invention.
Table 1 shows the joining strength of the obtained composite plate after joining. Table 1
As can be seen from the above, the composite plate manufactured within the scope of the present invention exhibits excellent bonding strength.

[Example 2] Using the iron layer and aluminum layer as shown in Table 2 as raw materials, the same heating temperature and sheet thickness reduction rate as shown in Table 2 were used. One side was an iron layer and the other side was an aluminum layer. The composite plates of layers were joined and allowed to cool. The aluminum layer used pure aluminum and various aluminum alloys as a joining material. These materials were wound in a coil shape and continuously heated by an apparatus as shown in FIG. 3 while unwinding the coil before joining. After heating, they were immediately overlaid and an external force was applied from both surfaces. External force was applied by the two rolls shown in FIG. 3 to join the plates continuously. The composite plate after joining was immediately forcibly cooled with gas at 15 ° C./s.

[0021]

[Table 2]

The joining conditions of Sample Nos. 1 to 10 are all within the scope of the present invention, and the joining conditions of Sample Nos. 11 to 18 are outside the scope of the present invention. Table 2 shows the bonding strength of the obtained composite plate after the bonding. As can be seen from Table 2, the composite plate manufactured within the scope of the present invention exhibits excellent bonding strength.

In the electric heating and pressure welding equipment shown in FIG. 3, electric current rolls 11 and 12 are provided on the iron layer 1 and the aluminum layer 2 of the raw material, respectively, and between the two rolls 4 which both perform electric current and pressure. The composite plate 5 is manufactured by continuously feeding the composite plate 5. As the power source, either a low frequency AC power source or a DC power source can be used. The current of the power source 21 is the current-carrying roll 11 on the iron layer 1.
Passes through the iron layer 1 and the aluminum layer 2 and reaches the energization roll 12 of the iron layer 1. In this case, since the iron layer has a higher electric resistance than the aluminum layer, when the thickness of the iron layer is the same as or thinner than that of the aluminum layer, the iron layer generates more heat and becomes hot. If the heating temperature of the iron layer does not reach the target temperature, the auxiliary power is supplied from the auxiliary power source 23 provided for auxiliary heating to the auxiliary roll to perform auxiliary heating.

[0024]

As described above, the composite plate of the iron plate and the aluminum plate manufactured by the present invention has excellent bonding strength.

[Brief description of drawings]

FIG. 1 is a diagram showing an influence of a thickness reduction rate of a composite plate upon bonding on the bonding strength of the composite plate.

FIG. 2 is a view showing an example of an apparatus that can be used for manufacturing a composite plate composed of an aluminum plate in the center and iron plates on both sides.

FIG. 3 is a diagram showing an example of an apparatus that can be used to manufacture a composite plate having two layers of an aluminum plate on one side and an iron plate on one side.

[Explanation of symbols]

 1,3 Iron layer 2 Aluminum layer 4 Roll (energization, pressurization) 5 Composite plate 11,12,13 Energizing roll 14,15 Auxiliary energizing roll 21,22 Power supply 23,24 Auxiliary power supply

Front Page Continuation (72) Inventor Hatsuhiko Oikawa 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd.

Claims (2)

[Claims] 1. When manufacturing a composite metal plate comprising three layers of which both surfaces are iron and the center is aluminum, an iron layer is formed on a 670 layer.
The aluminum layer is heated to 550 ° C. or higher and 1050 ° C. or lower and the aluminum layer is set to 550 ° C. or lower, and when both layers are in these temperature ranges, they are superposed, and an external force is immediately applied from both surfaces,
Manufacture of a composite metal plate with excellent bonding strength, characterized in that the reduction rate of the aluminum layer thickness due to an external force is 2% or more with respect to the thickness of the aluminum layer before the external force is applied, and then it is allowed to cool or forcedly cool Method. 2. When manufacturing a composite metal plate having two layers of which one side is iron and one side is aluminum, the iron layer is 670 ° C.
The aluminum layer is heated to 1050 ° C. or lower and the aluminum layer is heated to 550 ° C. or lower. When all layers are in these temperature ranges, the layers are superposed and an external force is immediately applied from both surfaces to reduce the plate thickness reduction rate of the aluminum layer by the external force. To 2% or more with respect to the plate thickness of the aluminum layer before adding, and then allowing to cool or forcibly cool the composite metal plate having excellent bonding strength.